1. On unitary couplings of semi-unitary operators;Adamjan;Amer. Math. Soc. Transl.,1970
2. On stability of some properties of orthogonal systems;Bari;Dokl. Akad. Nauk SSSR,1941
3. Sur les systèmes complets de fonctions orthogonales;Bari;Mat. Sb. Akad. Nauk SSSR,1944
4. Biorthogonal systems and bases in Hilbert space;Bari;Uchen. Zap. Moskov. Gos. Univ. Mat.,1951