Egni a bywyd /
Williams, Howard.
National Language Unit of Wales.
Caerdydd : Uned Iaith Genedlaethol Cymru CBAC,
1996.
Original Enlgish ed.: Cambridge : Cambridge University Press, 1983.
At head of cover title: Rhaglen Ddatblygu Addysg Hyblyg.
Bioenergetics.
Biology