The National Digital Heritage Archive of the Republic of Eldoria is undertaking a project to preserve digital collections of folklore from its diverse cultural groups. Eldoria\'s linguistic landscape includes several macrolanguages with numerous distinct dialects and closely related languages. A new national heritage act mandates that all digital archives must ensure long-term preservation and accessibility of cultural heritage materials, including accurate linguistic representation. The archive\'s initial proposal suggested using ISO 639-1 and ISO 639-2 language codes for cataloging the folklore collections. Dr. Anya Petrova, a leading linguist advising the project, raises concerns about the limitations of these standards in accurately representing the linguistic diversity. Considering the legal mandate and the need for precise linguistic identification for long-term preservation and accessibility, which ISO 639 standard, supplemented by what additional measure if necessary, would be most appropriate for the Eldorian National Digital Heritage Archive to adopt for cataloging its folklore collections?