@other{https://authors.library.caltech.edu/records/ytzcd-nm557,
    author = "Marble, F. E.",
    title = "Spacecraft Propulsion",
    year = "2015",
    url = "https://resolver.caltech.edu/CaltechAUTHORS:20151124-152119107",
    id = "https://authors.library.caltech.edu/records/ytzcd-nm557"
}