TY  - RPRT
TI  - A variational principle in optics.
AU  - Jacob Rubinstein
AU  - Gershon Wolansky
PY  - 2004
DO  - 10.1364/josaa.21.002164
UR  - https://pubmed.ncbi.nlm.nih.gov/15535374/
ID  - 15535374
ER  -