1. J. van Benthem, The semantics of variety in categorial grammar, In: W. Buszkowski, W. Marciszewski, J. van Benthem (eds.), Categorial Grammar, J. Benjamins, Amsterdam-Philadelphia 1988.
2. W. Buszkowski, The logic of types, In: J. Srzednicki (ed.), Initiatives in Logic, M. Nijhoff, Amsterdam 1987.
3. G. Gentzen, Untersuchungen ueber das logische Schliessen, Mathematische Zeitschrift 39 (1935), pp. 176?210, 405?431.
4. M. Kàndulski, The non-associative Lambek calculus, In: W. Buszkowski, W. Marciszewski, J. van Benthem (eds.), Categorial Grammar, J. Benjamins, Amsterdam 1988.
5. J. Lambek, The mathematics of sentence structure, American Mathematical Monthly 65 (1958), pp. 154?170.