E.M. McMillian, JASA Vol 18 #2, Oct 1946, page 344+

Lampton and Burk,
"Time reversal and reciprocity"
Acustica vol 56, 1984, page 23-28.

@article{Onsager31a
,author={Onsager, Lars}
,title={Reciprocal relations in irreversible processes. {I}.}
,journal=PHYREV
,year=1931
,month=feb
,volume={37}
,number={}
,pages={405--426}
,note={} }