Reference LGR for script: Telugu (Telu) lgr-second-level-telugu-script-24jan24-en

This document is mechanically formatted from the above XML file for the LGR. It provides additional summary data and explanatory text. The XML file remains the sole normative specification of the LGR.

Date 2024-01-24
LGR Version 2 (Second Level Reference LGR)
Language und-Telu (Telugu Script)
Unicode Version 11.0.0



  • These instructions cover how to adopt an LGR based on this reference LGR for a given zone and how to prepare the file for deposit in the IANA Repository of IDN Practices.
  • As described the IANA procedure
    an LGR MUST contain the following elements in its header:
    • Script or Language Designator (see below for guidance)
    • Version Number (this must increase with each amendment to the LGR, even if the updates are limited to the header itself)
    • Effective Date (the date at which the policy becomes applicable in operational use)
    • Registry Contact Details (contact name, email address, and/or phone number)
  • The following information is optional:
    • Document creation date
    • Applicable Domain(s)
    • Changes made to the Reference LGR before adopting

Please add or modify the following items in the XML source code for this file before depositing the document in the IANA Repository.

Meta Data

Note: version numbers start at 1. RFC 7940 recommends using simple integers. The version comment is optional, please replace or delete the default comment. Version comments may be used by some tools as part of the page header.

<version comment="[Please replace (or delete) the optional comment]">[Please fill in version number, starting at 1]</version>

<date>[Please fill in with publication date, in YYYY-MM-DD format]</date>

<validity-start>[Please fill in effective date, in YYYY-MM-DD format]</validity-start>

Note: the scope element may be repeated, so that the same document can serve for multiple domains.

<scope type="domain">[Please provide, in ".domain" format]</scope>

Registry Contact Information:

Please fill in the Registry Contact Details.

Change History

If you made technical modifications to the LGR, please summarize them in the Change History (and also note the details in the appropriate section of the description).


Registry Contact Details

Label Generation Rules for the Telugu Script


This document specifies a set of Label Generation Rules (LGR) for the Telugu script for the second level domain or domains identified above. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Telu]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Telugu Script” [Ref-LGR-und-Telu], for details, see Change History below.

For details and additional background on the Telugu script, see “Proposal for a Telugu Script Root Zone Label Generation Ruleset (LGR)” [Proposal-Telugu].


The repertoire contains 63 code points for letters catering to the Telugu language written using the Telugu script. Several other languages with [EGIDS] levels above 4 were also considered in the analysis. The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Telugu]. (The proposal cited has been adopted for the Telugu script portion of the Root Zone LGR.)

For the second level, the repertoire has been augmented with the ASCII digits, U+0030 0 to U+0039 9, plus U+002D - HYPHEN-MINUS, for a total of 74 repertoire elements.

Any code points outside the Telugu Script repertoire that are targets for out-of-repertoire variants would be included here only if the variant is listed in this file. In this case they are identified as a reflexive (identity) variant of type “out-of-repertoire-var”. Whether or not they are listed, they do not form part of the repertoire.

Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used, one or more tag values denoting character category, and one or more references documenting sufficient justification for inclusion in the repertoire, see “References” below. Comments provide alternate names for some code points.


The variants defined in this LGR are limited to those required for use in zones not shared with any other script. As such, this LGR does not define cross-script variants. However, using this LGR concurrently with any LGR for Kannada in the same zone will create potential cross-script issues. For details, see Section 6, “Variants” in [Proposal-Telugu]. Mitigation of these cross-script variants can be addressed by using the Common LGR. For details, see Section 3, “Use of Multiple Reference LGRs in the Same Zone” in [Level-2-Overview]. In addition to variants defined by this LGR, the full variant information related to this script and required for concurrent use with the Kannada LGR(s) can be found in the following LGR: [Ref-LGR-Telugu-Full-Variant-Script]

There are no in-script variants defined for Telugu. For details, see Section 6, “Variants” in [Proposal-Telugu].

Digit Variants: The Telugu reference LGR does not include native digits, so there are no semantic variants defined.

By transitivity, all ASCII digits are semantic variants of any cross-script native digits. Any Telugu label that is otherwise a cross-script variant of a label in another script, will remain a variant if both labels add digits of the same value in the same position, irrespective of whether they are ASCII digits or (in the case of the other script) native digits.

Variant Disposition: All variants are of type “blocked”, making labels that differ only by these variants mutually exclusive: whichever label containing either of these variants is chosen earlier would be delegated, while any other equivalent labels should be blocked. There is no preference among these labels.

This LGR does not define allocatable variants.

The specification of variants in this LGR follows the guidelines in [RFC 8228].

Character Classes

The Telugu orthography superficially resembles a series of circles and semi-circles. Most consonants carry a tick mark called ‘talakattu’. The writing system is classified as abugida type or alphasyllabary. The alphabet consists of vowels, consonants and modifiers. Each of these vowels and consonants has one or more secondary allographs.

Consonants: The Telugu consonants contain an implicit vowel /a/. More details in Section 3.5.4, “The Consonants” in [Proposal-Telugu].

Vowels and dependent vowel signs: There are fourteen vowel characters in the common inventory of which one is rarely used: U+0C0C . It and the two obsolete vowels, U+0C60 and U+0C61 , are excluded from this LGR. Each vowel, except U+0C05 has a dependent vowel sign, modifying the vowel of the consonant they follow. These signs may have different appearance depending on the size and shape of the consonant that functions as an anchor. More details in Section 3.5.1, “The vowels and vowel modifiers” in [Proposal-Telugu].

Anusvara or sunna: The Anusvara or sunna represents a homorganic nasal before the corresponding consonant and as a substitute to transcribe word final /mu/. Essentially, it substitutes a cluster of a Nasal Consonant+Halant before a consonant. More details in Section 3.5.2, “The Anusvara or sunna” in [Proposal-Telugu].

Visarga: Visarga denotes the glottal check.

Halant: A special sign is needed whenever the implicit vowel in the preceding consonant is stripped off. This symbol is known as the Halant. (Any vowel sign will also override the implicit vowel). More details in Section 3.5.1, “The vowels and vowel modifiers” in [Proposal-Telugu].

Common Digits: U+0030 0 to U+0039 9 are the set of digits from the ASCII range.

Whole Label Evaluation (WLE) and Context Rules

Common Rules

By default, the LGR includes the rules and actions to implement the following restrictions mandated by the IDNA protocol. They are marked with ⍟.

  • Hyphen Restrictions — restrictions on the allowable placement of hyphens (no leading/ending hyphen and no hyphen in positions 3 and 4). These restrictions are described in Section of RFC 5891 [150]. They are implemented here as context rule on U+002D (-) HYPHEN-MINUS.
  • Leading Combining Marks — restrictions on the allowable placement of combining marks (no leading combining mark). This rule is described in Section of RFC 5891 [150].

Default Actions

This LGR includes the default actions for LGRs as well as the action needed to invalidate labels with misplaced combining marks. They are marked with ⍟. For a description see [RFC 7940].

Telugu-specific Rules

These rules have been formulated so that they can be adopted for LGR specification.

The following symbols are used in the WLE rules:
C → Consonant
M → Matra (Dependent vowel signs)
V → Vowel
B → Anusvara (Bindu)
X → Visarga
H → Halant / Virama

The rules are:

  • 1. H: must be preceded by C
  • 2. M: must be preceded by C
  • 3. X: must be preceded by V, M or C
  • 4. B: must be preceded by V, M or C
  • 6. V: cannot be preceded by H

More details in Section 7, “Whole Label Evaluation Rules (WLE)” in [Proposal-Telugu]. The numbering of the rules given here, follows that document.

Methodology and Contributors

The LGR in this document has been adapted from the corresponding Reference LGR for the Second Level. The Second Level Reference LGR for the Telugu Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Telugu script and information contained or referenced therein; see [RZ-LGR-Telu]. Suitable extensions for the second level have been applied according to the [Guidelines] and with community input. The original proposal for a Root Zone LGR for the Telugu script, that this reference LGR is based on, was developed by the Neo-Brahmi Generation Panel (NBGP). For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Telugu], as well as [RZ-LGR-Overview].

Changes from Version Dated 15 December 2020

Unicode Version has been updated.

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Telugu Script [Ref-LGR-und-Telu] without normative changes.


The following general references are cited in this document:

Lewis and Simons, “EGIDS: Expanded Graded Intergenerational Disruption Scale,” documented in [SIL-Ethnologue] and summarized here:
ICANN, “Guidelines for Developing Reference LGRs for the Second Level”, (Los Angeles, California: ICANN, 27 May 2020),
Internet Corporation for Assigned Names and Numbers, (ICANN),“Reference Label Generation Rules (LGR) for the Second Level: Overview and Summary” (PDF), (Los Angeles, California: ICANN, 24 January 2024),
Neo-Brahmi Generation Panel, “Proposal for a Telugu Script Root Zone Label Generation Ruleset (LGR)”, 7 June 2019,
[RFC 7940]
Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
[RFC 8228]
A. Freytag, “Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels”, RFC 8228, August 2017,
ICANN, Second Level Reference Label Generation Rules for the Telugu Script (und-Telu), 24 January 2024 (XML)
non-normative HTML presentation:
ICANN, Second Level Reference Label Generation Rules for the Telugu Script (und-Telu), 24 January 2024 (XML)
non-normative HTML presentation:
Integration Panel, “Root Zone Label Generation Rules (RZ LGR-5): Overview and Summary”, 26 May 2022 (PDF),
ICANN, Root Zone Label Generation Rules for the Telugu Script (und-Telu), 26 May 2022 (XML)
David M. Eberhard, Gary F. Simons & Charles D. Fennig (eds.). 2021. Ethnologue: Languages of the World, Twenty fourth edition. Dallas, Texas: SIL International. Online version available as
[Unicode 11.0.0]
The Unicode Consortium. The Unicode Standard, Version 11.0.0, (Mountain View, CA: The Unicode Consortium, 2018. ISBN 978-1-936213-19-1)

For references consulted particularly in designing the repertoire for the Telugu Script for the second level please see details in the Table of References below.

Reference [0] refers to the Unicode Standard version in which the corresponding code points were initially encoded. References [102] and above correspond to sources given in [Proposal-Telugu] justifying the inclusion of the corresponding code points. Entries in the table may have multiple source reference values. In the listing of whole label evaluation and context rules, reference [150] indicates the source for common rules.


Repertoire Summary

Number of elements in repertoire 74
Number of code points
for each script
Telugu 63
Common 11
Longest code point sequence 1

Repertoire by Code Point

The following table lists the repertoire by code point (or code point sequence). The data in the Script and Name column are extracted from the Unicode character database. Where a comment in the original LGR is equal to the character name, it has been suppressed.

See also the legend provided below the table.

Glyph Script Name Ref Tags Required Context Comment
U+002D - Common HYPHEN-MINUS [0]   not: hyphen-minus-disallowed
U+0030 0 Common DIGIT ZERO [0] Common-digit  
U+0031 1 Common DIGIT ONE [0] Common-digit  
U+0032 2 Common DIGIT TWO [0] Common-digit  
U+0033 3 Common DIGIT THREE [0] Common-digit  
U+0034 4 Common DIGIT FOUR [0] Common-digit  
U+0035 5 Common DIGIT FIVE [0] Common-digit  
U+0036 6 Common DIGIT SIX [0] Common-digit  
U+0037 7 Common DIGIT SEVEN [0] Common-digit  
U+0038 8 Common DIGIT EIGHT [0] Common-digit  
U+0039 9 Common DIGIT NINE [0] Common-digit  
U+0C02  ం Telugu TELUGU SIGN ANUSVARA [0], [102], [103] Anusvara follows-V-M-or-C = sunna
U+0C03  ః Telugu TELUGU SIGN VISARGA [0], [102], [103] Visarga follows-V-M-or-C  
U+0C05 Telugu TELUGU LETTER A [0], [102], [103] Vowel not: follows-H  
U+0C06 Telugu TELUGU LETTER AA [0], [102], [103] Vowel not: follows-H  
U+0C07 Telugu TELUGU LETTER I [0], [102], [103] Vowel not: follows-H  
U+0C08 Telugu TELUGU LETTER II [0], [102], [103] Vowel not: follows-H  
U+0C09 Telugu TELUGU LETTER U [0], [102], [103] Vowel not: follows-H  
U+0C0A Telugu TELUGU LETTER UU [0], [102], [103] Vowel not: follows-H  
U+0C0B Telugu TELUGU LETTER VOCALIC R [0], [102], [103] Vowel not: follows-H  
U+0C0E Telugu TELUGU LETTER E [0], [102], [103] Vowel not: follows-H  
U+0C0F Telugu TELUGU LETTER EE [0], [102], [103] Vowel not: follows-H  
U+0C10 Telugu TELUGU LETTER AI [0], [102], [103] Vowel not: follows-H  
U+0C12 Telugu TELUGU LETTER O [0], [102], [103] Vowel not: follows-H  
U+0C13 Telugu TELUGU LETTER OO [0], [102], [103] Vowel not: follows-H  
U+0C14 Telugu TELUGU LETTER AU [0], [102], [103] Vowel not: follows-H  
U+0C15 Telugu TELUGU LETTER KA [0], [102], [103] Consonant    
U+0C16 Telugu TELUGU LETTER KHA [0], [102], [103] Consonant    
U+0C17 Telugu TELUGU LETTER GA [0], [102], [103] Consonant    
U+0C18 Telugu TELUGU LETTER GHA [0], [102], [103] Consonant    
U+0C19 Telugu TELUGU LETTER NGA [0], [102], [103] Consonant    
U+0C1A Telugu TELUGU LETTER CA [0], [102], [103] Consonant    
U+0C1B Telugu TELUGU LETTER CHA [0], [102], [103] Consonant    
U+0C1C Telugu TELUGU LETTER JA [0], [102], [103] Consonant    
U+0C1D Telugu TELUGU LETTER JHA [0], [102], [103] Consonant    
U+0C1E Telugu TELUGU LETTER NYA [0], [102], [103] Consonant    
U+0C1F Telugu TELUGU LETTER TTA [0], [102], [103] Consonant    
U+0C20 Telugu TELUGU LETTER TTHA [0], [102], [103] Consonant    
U+0C21 Telugu TELUGU LETTER DDA [0], [102], [103] Consonant    
U+0C22 Telugu TELUGU LETTER DDHA [0], [102], [103] Consonant    
U+0C23 Telugu TELUGU LETTER NNA [0], [102], [103] Consonant    
U+0C24 Telugu TELUGU LETTER TA [0], [102], [103] Consonant    
U+0C25 Telugu TELUGU LETTER THA [0], [102], [103] Consonant    
U+0C26 Telugu TELUGU LETTER DA [0], [102], [103] Consonant    
U+0C27 Telugu TELUGU LETTER DHA [0], [102], [103] Consonant    
U+0C28 Telugu TELUGU LETTER NA [0], [102], [103] Consonant    
U+0C2A Telugu TELUGU LETTER PA [0], [102], [103] Consonant    
U+0C2B Telugu TELUGU LETTER PHA [0], [102], [103] Consonant    
U+0C2C Telugu TELUGU LETTER BA [0], [102], [103] Consonant    
U+0C2D Telugu TELUGU LETTER BHA [0], [102], [103] Consonant    
U+0C2E Telugu TELUGU LETTER MA [0], [102], [103] Consonant    
U+0C2F Telugu TELUGU LETTER YA [0], [102], [103] Consonant    
U+0C30 Telugu TELUGU LETTER RA [0], [102], [103] Consonant    
U+0C32 Telugu TELUGU LETTER LA [0], [102], [103] Consonant    
U+0C33 Telugu TELUGU LETTER LLA [0], [102], [103] Consonant    
U+0C35 Telugu TELUGU LETTER VA [0], [102], [103] Consonant    
U+0C36 Telugu TELUGU LETTER SHA [0], [102], [103] Consonant    
U+0C37 Telugu TELUGU LETTER SSA [0], [102], [103] Consonant    
U+0C38 Telugu TELUGU LETTER SA [0], [102], [103] Consonant    
U+0C39 Telugu TELUGU LETTER HA [0], [102], [103] Consonant    
U+0C3E  ా Telugu TELUGU VOWEL SIGN AA [0], [102], [103] Matra follows-C  
U+0C3F  ి Telugu TELUGU VOWEL SIGN I [0], [102], [103] Matra follows-C  
U+0C40  ీ Telugu TELUGU VOWEL SIGN II [0], [102], [103] Matra follows-C  
U+0C41  ు Telugu TELUGU VOWEL SIGN U [0], [102], [103] Matra follows-C  
U+0C42  ూ Telugu TELUGU VOWEL SIGN UU [0], [102], [103] Matra follows-C  
U+0C43  ృ Telugu TELUGU VOWEL SIGN VOCALIC R [0], [102], [103] Matra follows-C  
U+0C44  ౄ Telugu TELUGU VOWEL SIGN VOCALIC RR [0], [102], [103] Matra follows-C  
U+0C46  ె Telugu TELUGU VOWEL SIGN E [0], [102], [103] Matra follows-C  
U+0C47  ే Telugu TELUGU VOWEL SIGN EE [0], [102], [103] Matra follows-C  
U+0C48  ై Telugu TELUGU VOWEL SIGN AI [0], [102], [103] Matra follows-C  
U+0C4A  ొ Telugu TELUGU VOWEL SIGN O [0], [102], [103] Matra follows-C  
U+0C4B  ో Telugu TELUGU VOWEL SIGN OO [0], [102], [103] Matra follows-C  
U+0C4C  ౌ Telugu TELUGU VOWEL SIGN AU [0], [102], [103] Matra follows-C  
U+0C4D  ్ Telugu TELUGU SIGN VIRAMA [0], [102], [103] Halant follows-C = halant


Code Point
A code point or code point sequence.
The shape displayed depends on the fonts available to your browser.
Shows the script property value from the Unicode Character Database. Combining marks may have the value Inherited and code points used with more than one script may have the value Common.
Shows the character or sequence name from the Unicode Character Database.
Links to the references associated with the code point or sequence, if any.
LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view.
Required Context
Link to a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:” identifies a context that must not occur.
The comment as given in the XML file. However, if the comment for this row consists only of the code point or sequence name, it is suppressed in this view. By convention, comments starting with “=” denote an alias. If present, the symbol ⍟ marks a default item shared among a set of LGRs.


This LGR does not specify any variants.

Classes, Rules and Actions

Character Classes

Number of named classes 4
Implicit (except script) 3
Implict defined by script tag 2

The following table lists all named and implicit classes with their definition and a list of their members intersected with the current repertoire (for larger classes, this list is elided).

Name Definition Count Members or Ranges Ref Comment
C Tag=Consonant 34 {0C15-0C28 0C2A-0C30 0C32-0C33 0C35-0C39}   Any Telugu consonant
V Tag=Vowel 13 {0C05-0C0B 0C0E-0C10 0C12-0C14}   Any Telugu independent vowel
M Tag=Matra 13 {0C3E-0C44 0C46-0C48 0C4A-0C4C}   Any Telugu vowel sign (matra)
H Tag=Halant 1 {0C4D}   The Telugu Halant / Virama
implicit Tag=Anusvara 1 {0C02}   The character tagged as Anusvara
implicit Tag=Common-digit 10 {0030-0039}   Any character tagged as Common-digit
implicit Tag=Visarga 1 {0C03}   The character tagged as Visarga
implicit Tag=sc:Telu 63 {0C02-0C03 0C05-0C0B 0C0E-0C10 0C12-0C28 0C2A-0C30 0C32-0C33 0C35-0C39 0C3E-0C44 0C46-0C48 0C4A-0C4D}   Any character tagged as Telugu
implicit Tag=sc:Zyyy 11 {002D 0030-0039}   Any character tagged as Common


Members or Ranges
Lists the members of the class as code points (xxx) or as ranges of code points (xxx-yyy). Any class too numerous to list in full is elided with "...".
A named or implicit class defined by all code points that share the given tag value (ttt).
An anonymous class implicitly defined based on tag value and for which there is no named equivalent.

Whole label evaluation and context rules

Number of rules 5
Used to trigger actions 1
Used as context rule (C) 4
Anchored context rules 4

The following table lists all named rules defined in the LGR and indicates whether they are used as trigger in an action or as context (when or not-when) for a code point or variant.

Name Regular Expression Used as
Anchor Used as
Ref Comment
leading-combining-mark (start)[[\p{gc=Mn}] ∪ [\p{gc=Mc}]]     [150] RFC 5891 restrictions on placement of combining marks ⍟
hyphen-minus-disallowed (((start))← ⚓︎)|(⚓︎ →((end)))|(((start)..\u002D)← ⚓︎)   C [150] RFC 5891 restrictions on placement of U+002D -
follows-C ([:C:])← ⚓︎   C   Section 7, WLE 1: H must be preceded by a C; WLE 2: M must be preceded by C
follows-V-M-or-C ([:V:]|[:M:]|[:C:])← ⚓︎   C   Section 7, WLE 3: Visarga must be preceded by V, M or C; WLE 4: Anusvara must be preceded by V, M or C
follows-H ([:H:])← ⚓︎   C   Section 7, WLE 6: V cannot be preceded by H


Used as Trigger
This rule triggers one of the actions listed below.
Used as Context
This rule defines a required or prohibited context for a code point C or variant V.
This rule has a placeholder for the code point for which it is evaluated.
Regular Expression
A regular expression equivalent to the rule, shown in a modified notation as noted:
⚓︎ - context anchor
Placeholder for the actual code point when a context is evaluated. The code point must occur at the position corresponding to the anchor. Rules containing an anchor cannot be used as triggers.
(...)← - look-behind
If present encloses required context preceding the anchor.
→(..) - look-ahead
If present encloses required context following the anchor.
( ) - group
An anonymous nested rule is used to group match operators.
(... | ...) - choice
When there is more than one alternative in a rule, the choices are separated by the alternation operator (...|...).
start or end
(start) matches the start of the label; (end) matches the end of the label.
. - any code point
. matches any code point.
[: :] - named or implicit character set
Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
[\p{ }] - property
Set of all characters matching a given value for a Unicode property [\p{prop=val}]. Note: uppercase “\P” defines the complement of a property set.
∪, ∩, ∖, ∆ - set operators
Sets may be combined by set operators ( = union, = intersection, = difference, = symmetric difference).
⍟ - default rule
Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.


The following table lists the actions that are used to assign dispositions to labels and variant labels based on the specified conditions. The order of actions defines their precedence: the first action triggered by a label is the one defining its disposition.

# Condition Rule / Variant Set   Disposition Ref Comment
1 if label matches leading-combining-mark invalid [150] labels with leading combining marks are invalid ⍟
2 if at least one variant is in {out-of-repertoire-var} invalid   any variant label with a code point out of repertoire is invalid ⍟
3 if at least one variant is in {blocked} blocked   any variant label containing blocked variants is blocked ⍟
4 if each variant is in {allocatable} allocatable   variant labels with all variants allocatable are allocatable ⍟
5 if any label (catch-all)   valid   catch all (default action) ⍟


{...} - variant type set
In the “Rule/Variant Set” column, the notation {...} means a set of variant types.
⍟ - default action
Actions marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, blocked, out-of-repertoire-var. This is not necessarily an error.

Table of References

The following lists the references cited for specific code points, variants, classes, rules or actions in this LGR. For General references refer to the References section in the Description.

[0] The Unicode Standard, Version 1.1
Any code point originally encoded in Unicode 1.1
[102] Krishnamurti, Bhadriraju (Ed.). 2000. Telugu bhaashaa charitra. Hyderabad: P.S. Telugu University. (first edition 1974)
[103] Krishnamurti, Bhadriraju and J P L Gwynn. 1985. A Grammar of Modern Telugu. New Delhi: Oxford University Press. ISBN 978-0-19-561664-4
[150] RFC 5891, Internationalized Domain Names in Applications (IDNA): Protocol