Cita APA (7th ed.)

Webster, R. (1970). Gems : their sources, descriptions and: Identification. Butterworths.

Cita Chicago (17th ed.)

Webster, Robert. Gems : Their Sources, Descriptions and: Identification. London: Butterworths, 1970.

Cita MLA (9th ed.)

Webster, Robert. Gems : Their Sources, Descriptions and: Identification. Butterworths, 1970.