24 http://hdl.handle.net/10338.dmlcz/116830 1974 Book reviews. Proceedings of the Equadiff III http://hdl.handle.net/10338.dmlcz/101282 Book reviews. Proceedings of the Equadiff III A general coordinatization principle for projective planes with comparison of Hall and Hughes frames and with examples of generalized oval frames http://hdl.handle.net/10338.dmlcz/101281 A general coordinatization principle for projective planes with comparison of Hall and Hughes frames and with examples of generalized oval frames On the spectrum of a nonlinear operator http://hdl.handle.net/10338.dmlcz/101280 On the spectrum of a nonlinear operator Ternary rings with zero associated to Desarguesian and Pappian planes http://hdl.handle.net/10338.dmlcz/101279 Ternary rings with zero associated to Desarguesian and Pappian planes