Lewis, M. Paul; Gary F. Simons (2010),"Assessing Endangerment: Expanding Fishman’s GIDS", Revue Roumaine de linguistique 55(2), 103–120. xemLưu trữ 2015-12-27 tại Wayback Machine
Lewis, M. Paul; Gary F. Simons (2010),"Assessing Endangerment: Expanding Fishman’s GIDS", Revue Roumaine de linguistique 55(2), 103–120. xemLưu trữ 2015-12-27 tại Wayback Machine