Mathemateg pen : ar gyfer oedrannau 9 i 11  : llyfr athrawon /
Straker, Anita.
Trosol (Organization)
National Language Unit of Wales.
Welsh Joint Education Committee.
Caerdydd : Uned Iaith Genedlaethol Cymru,
1998.
Arg. Saesneg gwreiddiol = Original English ed.: Cambridge: Cambridge University Press, 1994
Addasiad Cymraeg gan = Welsh adaptation by: Trosol Cyf.
Mathematics
Mental arithmetic
Teaching