References
- Facchini , A. and Vàmos , P. 1985 . Injective modules over pullbacks , Vol. 31,2 , 425 – 438 . J.London Math. Soc. .
- Kaplanskey , I. 1974 . “ Commutative Rings ” . Allyn and Bacon . revised edition
- Man , S.H. 1991 . Finite projective dimension over pullbacks of local rings . Communications in Algebra , 19 : 3271 – 3294 .