1. Beidar, K.I.: Rings with generalized identities III. Moscow Univ. Math. Bull. 33, 53–58 (1978)
2. Beidar, K.I., Martindale, W.S., III., Mikhalev, A.V.: Rings with Generalized Identities. Pure and Applied Math, Dekker, New York (1996)
3. Chang, J.-C.: On the identitity $$h(x)=af(x)+g(x)b$$. Taiwanese J. Math. 7, 103–113 (2003)
4. Cheng, H.-W., Wei, F.: Generalized skew derivations of rings. Adv. Math. 35(2), 237–243 (2006)
5. Chuang, C.-L.: GPIs having coefficients in Utumi quotient rings. Proc. Amer. Mat. Soc. 103(3), 723–728 (1988)