@article{hilliard1969an, title = {An Improved Theater Type Loudspeaker System}, author = {Hilliard, John K.}, journal = {J. Audio Eng. Soc}, volume = {17}, number = {5}, pages = {512--514}, year = {1969}, url = {https://www.aes.org/e-lib/browse.cfm?elib=1560} }