TY  - RPRT
TI  - On equations with sets as unknowns.
AU  - P Erdös
AU  - S Ulam
PY  - 1968
DO  - 10.1073/pnas.60.4.1189
UR  - https://pubmed.ncbi.nlm.nih.gov/16591682/
ID  - 16591682
ER  -