Lavendhomme R., Lucas Th. and G. E. Reyes (1989). Formal systems for topos-
theoretic modalities. Bull. Soc. math. Belgique (serie A), XLI, Fascicule 2. 333-372.
From mathematics to literature. – Des mathématiques à la littérature.
Lavendhomme R., Lucas Th. and G. E. Reyes (1989). Formal systems for topos-
theoretic modalities. Bull. Soc. math. Belgique (serie A), XLI, Fascicule 2. 333-372.