TY  - RPRT
TI  - What is directionality?
AU  - S Greenland
AU  - H Morgenstern
PY  - 1989
DO  - 10.1016/0895-4356(89)90092-9
UR  - https://pubmed.ncbi.nlm.nih.gov/2778461/
ID  - 2778461
ER  -