@article{petrie1963compatibility, title = {Compatibility-A Major Requisite in the Telephone Industry}, author = {Petrie, Joseph N.}, journal = {J. Audio Eng. Soc}, volume = {11}, number = {2}, pages = {135--141}, year = {1963}, url = {https://www.aes.org/e-lib/browse.cfm?elib=806} }