www.wales.ac.uk/Resources/Documents/Research/CelticLanguages/EnglishProtoCelticWordList.pdf - An English to Proto-Celtic word list.
www.wales.ac.uk/Resources/Documents/Research/CelticLanguages/ProtoCelticEnglishWordlist.pdf - A Proto-Celtic to English word list.
archive.org/details/EtymologicalDictionaryOfProtoCeltic - Matasović, 'Etymological Dictionary Of Proto Celtic' (2017)