2 citations to https://www.mathnet.ru/rus/zvmmf7270

1. B. Mond, J.E. Pečarić, “An extension of the generalised schur inequality”, Bull. Austral. Math. Soc., 52:2 (1995), 341  
2. Khakim D. Ikramov, “A simple proof of the generalized Schur inequality”, Linear Algebra and its Applications, 199 (1994), 143