Timothy Smiley. On Łukasiewicz's Ł-modal system. Notre Dame Journal of Formal Logic, 2(3):149-153, 1961. [doi]
@article{Smiley61,
title = {On Łukasiewicz's Ł-modal system},
author = {Timothy Smiley},
year = {1961},
doi = {10.1305/ndjfl/1093956874},
url = {http://dx.doi.org/10.1305/ndjfl/1093956874},
researchr = {https://researchr.org/publication/Smiley61},
cites = {0},
citedby = {0},
journal = {Notre Dame Journal of Formal Logic},
volume = {2},
number = {3},
pages = {149-153},
}