@other{https://resolver.caltech.edu/CaltechETD:etd-08232004-105610,
    title = "Analysis and identification of linear and nonlinear normal modes in vibrating systems",
    year = "1991",
    url = "https://resolver.caltech.edu/CaltechETD:etd-08232004-105610",
    id = "record",
    doi = "10.7907/60CA-1Q64"
}