TY  - RPRT
TI  - Concurrent activity under fixed-interval reinforcement.
AU  - B F SKINNER
AU  - W H MORSE
PY  - 1957
DO  - 10.1037/h0047021
UR  - https://pubmed.ncbi.nlm.nih.gov/13463165/
ID  - 13463165
ER  -