Cita APA (7th ed.)

Harland, W. B. (1990). A geologic time scale 1989. C.U.Pr..

Cita Chicago (17th ed.)

Harland, W. Brian. A Geologic Time Scale 1989. Cambridge: C.U.Pr., 1990.

Cita MLA (9th ed.)

Harland, W. Brian. A Geologic Time Scale 1989. C.U.Pr., 1990.