As part of the continuous process of updating the DDC so that it remains consistent with the most current information available, the editors make constant use of a wide variety of authoritative reference works across the full range of subject areas that Dewey covers (i.e., everything). Over the next few months, the Dewey blog will be highlighting a few of the most useful of these reference sources -- starting today with a giant in the field of linguistics. Ethnologue: Languages of the world, 15th ed. (2005), edited by Raymond G. Gordon, Jr., and published by SIL International of Dallas, TX, is a compendium of information about 7,299 living languages that includes an index of 39,491 distinct names for those languages. The 1st edition of Ethnologue appeared in 1951; the 14th edition was published in 2000, and access is currently available, free-of-charge, to electronic versions of both the 14th and the 15th editions, on the web at http://www.ethnologue.com/. Ethnologue arranges individual languages in a hierarchy of families according to the relationships determined to exist between those languages, and the resulting tree structure is easily browsable at the web site. Dewey editors' development of the hierarchical structure of the DDC's Table 6 (Languages), and their decisions as to the location within this structure of individual languages and as to the preferred forms of language names that appear in DDC captions and indexing, have been informed by Ethnologue data since the preparation of DDC 20 (published in 1989). The recent mapping of the LC subject heading "Ngoni language (Tanzania and Mozambique)" to T6—96391 Central Bantu languages Central eastern Bantu languages, for instance, was done after consulting Ethnologue's "linguistic lineage" for Ngoni, which places it in the Manda group in zone N of the Narrow Bantu family of Niger-Congo languages. We don't always view Ethnologue as the final word, however: sometimes consultation with authorities in particular localities leads us to conclusions that differ from Ethnologue's. A case in point is our relocation of the South African language Ndebele to T6—963989, i.e., in the Nguni group (rather than the Sotho-Tswana group) in zone S of the Narrow Bantu family.