1. Valenta L., Vamanu D., Havlasová H.: to appear in the Proceeding of the International Conference on Magnetism, Grenoble, September 1970.
2. Tyablikov S. V.: Methods of the Quantum Theory of Magnetism. Nauka, Moscow 1965.
3. Valenta L.: to appear in the Proceedings of the International Conference on Magnetism, Grenoble, September 1970.
4. to be published in Acta Universitatis Carolinae, Prague.