Joshua Whatmough in R.S. Conway, J. Whatmough and S.E. Johnson, The Prae-Italic Dialects of Italy (London 1933) vol. 2:431-500; a more recent study is A
de Vaan, Michiel. 2008. Etymological dictionary of Latin and the other Italic languages. Leiden, The Netherlands: Brill. Martzloff, Vincent. "Questions