TY  - RPRT
TI  - Does conditional discrimination learning by pigeons necessarily involve hierarchical relationships?
AU  - D R Thomas
AU  - E K Schmidt
PY  - 1989
DO  - 10.1901/jeab.1989.52-249
UR  - https://pubmed.ncbi.nlm.nih.gov/16812596/
ID  - 16812596
ER  -