@other{https://resolver.caltech.edu/CaltechETD:etd-08092006-145027,
    title = "Calcium-Ion Exchange of Coal for Retention of Sulfur During Combustion",
    url = "https://resolver.caltech.edu/CaltechETD:etd-08092006-145027",
    id = "record",
    doi = "10.7907/X4W7-D106"
}