Indo-European Poetry and Myth - M L West
In Search of the Indo-Europeans: Language, Archaeology and Myth -  J.P Mallory
Mitra-Varuna: Essay on Two Indo-European Representations of Sovereignty - Georges Dumezil

Gods of the Celts - Miranda Green
Dying for the Gods - Miranda Green
Dictionary of Celtic myth & legend - Miranda Green
Exploring the world of the Celts - Simon James
Iron age communities in Britain - Barry Cunliffe
Gods with thunderbolts -  Guy de la Bedoyere
Pagan Celts - Anne Ross
Myths & legends of the Celts-  James Mackillop

The Mabinogion - Sioned Davies (trans.)
Legendary Poems from the Book of Taliesin - Marged Haycock
Trioedd ynys Prydein - Rachel Bromwich
Folklore of Wales - Marie Trevelyan

Dictionary of British Folk Tales - Katherine Briggs (4 vols)
The Silver Bough: Scottish Folk-Lore and Folk-Belief - F Marion McNeill
Scottish Wonder Tales from Myth and Legend - Donald A. Mackenzie
Scottish folk-lore and folk life : studies in race, culture and tradition - Donald Alexander Mackenzie

Celtic Heritage: Ancient Tradition in Ireland and Wales - Rees and Rees
Ireland and the Grail - John Carey
The Tain – Kinsella’s translation
Pagan Past and Christian Present in early Irish Literature - Kim McCone.
Early Christian Ireland -  Thomas Charles-Edwards.