Ethnologue: Languages of the World, 16th Edition (2009) . (2009) · edited by M. Paul Lewis · SIL International http://www.ethnologue.com/

Glottolog . http://www.glottolog.org/glottolog/

Pennsylvania German ( pp. 420-438 ch. 13 ) . Van Ness, Silke (1994) · In The Germanic Languages edited by König, Ekkehard and Johan van der Auwera · Routledge