Publications from 1987
Note that a paper may appear in listings for multiple years due to multiple publication (of tech. report, conference, and journal versions).On the NP-completeness of cryptarithms.
D. Eppstein.
SIGACT News 18 (3): 38–40, 1987.
A cryptarithm (also known as an alphametic) is a puzzle in which the digits of a mathematical formula (typically addition of two large numbers) are replaced by letters; the goal is to determine which letter stands for which digits. If arithmetic is done in a polynomially large radix, the problem becomes NP-complete.