Storrs McCall. A simple decision procedure for one-variable implicational/negation formulae in intuitionist logic. Notre Dame Journal of Formal Logic, 3(2):120-122, 1962. [doi]
@article{McCall62,
title = {A simple decision procedure for one-variable implicational/negation formulae in intuitionist logic},
author = {Storrs McCall},
year = {1962},
doi = {10.1305/ndjfl/1093957158},
url = {http://dx.doi.org/10.1305/ndjfl/1093957158},
researchr = {https://researchr.org/publication/McCall62},
cites = {0},
citedby = {0},
journal = {Notre Dame Journal of Formal Logic},
volume = {3},
number = {2},
pages = {120-122},
}