Roman Kontchakov, Agi Kurucz, Michael Zakharyaschev. Undecidability of first-order intuitionistic and modal logics with two variables. Bulletin of Symbolic Logic, 11(3):428, 2005. [doi]
@article{KontchakovKZ05,
title = {Undecidability of first-order intuitionistic and modal logics with two variables},
author = {Roman Kontchakov and Agi Kurucz and Michael Zakharyaschev},
year = {2005},
url = {http://www.math.ucla.edu/~asl/bsl/1103/1103-006.ps},
tags = {modal logic, logic},
researchr = {https://researchr.org/publication/KontchakovKZ05},
cites = {0},
citedby = {0},
journal = {Bulletin of Symbolic Logic},
volume = {11},
number = {3},
pages = {428},
}