Jarmila Panevová (1998):Ellipsis and zero elements in the structure of the sentence. In: Tipologija, grammatika, semantika. K 65-letiju Viktora Samuiloviča Chrakovskogo. (ed. N. A. Kozinceva, A.K. Ogloblin), Nauka, Sankt-Peterburg, ISBN 5-02-028355-X (bibtex)