1. L. G. Labsker and I. Rasa, “Tchebycheff systems: some criteria and properties. III,” Bull. Appl. Math. (Hungary),59, No. 736–750, 79–84 (1991).
2. I. Rasa, “A remark on Tchebycheff systems,” Anal. Numér. Théor. Approx.,6, No. 2, 193–195 (1977).
3. L. G. Labsker, “Characterization of Chebyshev systems and sufficient conditions for their nonextendability,” Dokl. Akad. Nauk SSSR,276, No. 2, 277–281 (1984).
4. L. G. Labsker, “On a certain criterion for Chebyshev systems,” Mat. Zametki,39, No. 2, 196–211 (1986).
5. L. G. Labsker and I. Rasa, “Tchebycheff systems: some criteria and properties. I,” Bull. Stiint. Inst. Politehn. Cluj-Napoca Ser. Mat. Mec. Apl. Construc. Mas.,33, 7–10 (1990).