MEDLINE and CANCERLIT databases were searched for published data. Searches were limited to articles published in English from 1980 onwards. Relevant references from articles found were also used. The following books were also used as research material for this review.
Cancer prevention and control. Greenwald P, Barnett S, Kramer BS, Weed DL (Eds). New York, NY: Marcel Dekker Inc, 1995.
Molecular pathology of cancer. Srivastava S, Hanson DE, Gazdar A (Eds). Amsterdam, Netherlands: IOS Press,