You might add to the list:
Dear Far Voiced Veteran - Essays in honour of Tom Munnelly Ed. Anne Clune, (mainly Ireland & UK) Pub. Old Kilfarboy Society 2007 (available from OAC website).
The Glenbuchat Ballads. Eds David Buchan and James Moreira, (Scotland) University Press of Mississippi 2007
A History of Europesn Folk Music, Jan Ling, University of Rochester Press
Jim Carroll