TY  - RPRT
TI  - Second-order conditioning with and without unconditioned stimulus presentation.
AU  - P C Holland
PY  - 1980
DO  - 10.1037//0097-7403.6.3.238
UR  - https://pubmed.ncbi.nlm.nih.gov/7391751/
ID  - 7391751
ER  -