TY  - RPRT
TI  - Dynamical Systems of Continuous Spectra.
AU  - B O Koopman
AU  - J V Neumann
PY  - 1932
DO  - 10.1073/pnas.18.3.255
UR  - https://pubmed.ncbi.nlm.nih.gov/16587673/
ID  - 16587673
ER  -