| (1c),(1d),(1e) | Summaries of articles published in this issue. | 
| 511-521 | Decompositions of the state space, homomorphisms and products of semigroup acts. Sikdar, Kripasindhu | 
| 522-527 | Quasi-reflections and limits. Skula, Ladislav | 
| 528-540 | Periodic solutions to a singular abstract differential equation. Straškraba, Ivan; Vejvoda, Otto | 
| 541-551 | Prime subgroups of ordered groups. Rachůnek, Jiří | 
| 552-562 | On compact $N$-semigroups. Hoo, Cheong Seng; Shum, Kar-Ping | 
| 563-572 | Addition linearer Cantormengen. Kahnert, Dietmar | 
| 573-583 | A new class of enumeration problems. Johnson, R. H. | 
| 584-597 | Relative boundedness conditions and the perturbation of nonlinear operators. Riedl, H. M.; Webb, Glenn F. | 
| 598-606 | Natural exactly covering systems of congruences. Porubský, Štefan | 
| 607-613 | Ternary rings with zero associated to Desarguesian and Pappian planes. Klucký, Dalibor | 
| 614-663 | On the spectrum of a nonlinear operator. Souček, Jiří; Souček, Vladimír | 
| 664-673 | A general coordinatization principle for projective planes with comparison of Hall and Hughes frames and with examples of generalized oval frames. Havel, Václav | 
| 674 | Book reviews. Proceedings of the Equadiff III. Kufner, Alois |