TY  - RPRT
TI  - NON-OBSTRUCTING SETS AND RELATED MAPPINGS.
AU  - G T Whyburn
PY  - 1960
DO  - 10.1073/pnas.46.9.1244
UR  - https://pubmed.ncbi.nlm.nih.gov/16590742/
ID  - 16590742
ER  -