ON JENSEN'S AND RELATED COMBINATORIAL IDENTITIES.

Motivated by the recent work of Chu [Electron. J. Combin. 17 (2010), #N24], we give simple proofs of Jensen's identity "Multiple line equation(s) cannot be represented in ASCII text; please see PDF of this article if available.", and Chu's and Mohanty-Handa's generalizations of Jensen's identity. We also give a simple proof of an equivalent form of Graham-Knuth- Patashnik's identity "Multiple line equation(s) cannot be represented in ASCII text; please see PDF of this article if available.", which was rediscovered, respectively, by Sun in 2003 and Munarini in 2005. Finally we give a multinomial coefficient generalization of this identity. [ABSTRACT FROM AUTHOR]