More Commentary on Missing Information in Relational Databases (Applicable and Inapplicable Information).

http://doi.acm.org/10.1145/24820.24823 db/journals/sigmod/Codd87.html E. F. Codd More Commentary on Missing Information in Relational Databases (Applicable and Inapplicable Information). 42-50 sigmodR/16-1/P042.pdf 1987 16 SIGMOD Record 1 db/journals/sigmod/sigmod16.html#Codd87