Griffiths, Bruce; Glyn Jones, Dafydd (1995), “arm”, inGeiriadur yr Academi: The Welsh Academy English–Welsh Dictionary[1], Cardiff: University of Wales Press,→ISBN
D. G. Lewis, N. Lewis, editors (2005–present), “arf”, inGweiadur: the Welsh–English Dictionary, Gwerin
R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke et al., editors (1950–present), “arf”, inGeiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies