Michael A. Gilbert. A heuristic procedure for natural deduction derivations using reductio ad absurdum. Notre Dame Journal of Formal Logic, 17(4):638-639, 1976. [doi]
@article{Gilbert76,
title = {A heuristic procedure for natural deduction derivations using reductio ad absurdum},
author = {Michael A. Gilbert},
year = {1976},
doi = {10.1305/ndjfl/1093887736},
url = {http://dx.doi.org/10.1305/ndjfl/1093887736},
researchr = {https://researchr.org/publication/Gilbert76},
cites = {0},
citedby = {0},
journal = {Notre Dame Journal of Formal Logic},
volume = {17},
number = {4},
pages = {638-639},
}