Frank D. Linn. Missing and Inapplicable Values. SIGMOD Record, 16(2):18-19, 1987. [doi]
@article{Linn87-0, title = {Missing and Inapplicable Values}, author = {Frank D. Linn}, year = {1987}, doi = {10.1145/988598.988599}, url = {http://doi.acm.org/10.1145/988598.988599}, researchr = {https://researchr.org/publication/Linn87-0}, cites = {0}, citedby = {0}, journal = {SIGMOD Record}, volume = {16}, number = {2}, pages = {18-19}, }