TY  - RPRT
TI  - The second filter is real, but how does it work?
AU  - H Davis
PY  - 1981
DO  - 10.1016/s0196-0709(81)80034-8
UR  - https://pubmed.ncbi.nlm.nih.gov/7270803/
ID  - 7270803
ER  -