Here are entered works on the simultaneous coexistence of two forms of the same language in a speech community. Works on switching from one language to another by bilingual members of a speech community are entered under the heading Code switching (Linguistics)
Code switching (Linguistics) -- Caribbean Area : Spanish-English codeswitching in the Caribbean and the US / edited by Rosa E. Guzzardo Tamargo, Catherine M. Mazak, M. Carmen Parafita Couto
Code switching (Linguistics) -- Egypt : Code-switching with the gods : the bilingual (Old Coptc-Greek) spells of PGM IV (P. Bibliothèque Nationale Supplément Grec. 574) and their linguistic, religious, and socio-cultural context in late Roman Egypt / Edqard O.D. Love
Code switching (Linguistics) -- Germany. : Discursive constructions of immigrant identity : a sociolinguistic trend study on long-term American immigrants / Inke Du Bois
Code switching (Linguistics) -- Israel : Codeswitching as an index and construct of sociopolitical identity : the case of the Druze and Arabs in Israel / by Eve Afifa Kheir
Code switching (Linguistics) -- Wales : Building and using the Siarad corpus : bilingual conversations in Welsh and English / Margaret Deuchar, Peredur Webb-Davies, Kevin Donnelly