Põhjaeesti keskmurre : häälikulisi ja morfoloogilisi peajooni

The source material for the study consisted of handwritten phonetic and morphological surveys of Estonian dialects preserved in the archives of the Institute of Language and Literature — now the Institute of the Estonian Language — and in the dialect archive of the Department of Estonian at University of Tartu. These included summaries and studies produced as university seminar papers, diploma theses, candidate dissertations, master’s theses, and doctoral dissertations. Additional data were drawn from dialect texts recorded in the Central Estonian dialect area, vocabulary collections, audio recordings made during dialect field expeditions, published editions of folk songs from the same region, and linguistic publications.