1. N. Burshtein, Oral communication to P. Erdös, Nice, September 1970.
2. N. Burshtein and J. Schönheim, Some results on exactly covering systems of congruences having moduli occuring at most twice, to appear.
3. On the solutions in integers of a⧸b=x-11 + … + x-1n;Erdös;Mat. Lapok,1950
4. On a problem concerning congruence systems;Erdös;mat. Lapok,1952