Paul J. Campbell. An answer to Armstrong's question about incompleteness in Copi: "A question about incompleteness". Notre Dame Journal of Formal Logic, 18(2):262-264, 1977. [doi]
@article{Campbell77,
title = {An answer to Armstrong's question about incompleteness in Copi: "A question about incompleteness"},
author = {Paul J. Campbell},
year = {1977},
doi = {10.1305/ndjfl/1093887931},
url = {http://dx.doi.org/10.1305/ndjfl/1093887931},
researchr = {https://researchr.org/publication/Campbell77},
cites = {0},
citedby = {0},
journal = {Notre Dame Journal of Formal Logic},
volume = {18},
number = {2},
pages = {262-264},
}