@other{https://resolver.caltech.edu/CaltechTHESIS:04082013-143307592,
    title = "Wave propagation in an inhomogeneous medium",
    year = "1968",
    url = "https://resolver.caltech.edu/CaltechTHESIS:04082013-143307592",
    id = "record",
    doi = "10.7907/CQ38-0N14"
}