@article{BSL3_2_Porebska_Wronski,
author = {Ma{\l}gorzata T. POR{\k{E}}BSKA and Andrzej WRO{\'N}SKI},
title = {A Characterization of Fragments of the Intuitionistic Propositional Logic},
journal = {Bulletin of the Section of Logic},
volume = {3},
number = {2},
year = {1974},
pages = {19--20}
}