2. Black WC, Welch HG. Screening for disease. AJR 997;01. 168:3-11.
3. Feightner JW, Battista RN, Dingle JL. In: Rakel RE, editor. Periodic health examination. Textbook of Family Medicine 1995;5th ed. Philadelphia: Saunders. 165-191.
4. The periodic health examination. Canadian Task Force on the Periodic Health Examination. Can Med Assoc J 1979;121:1193-1254.
5. U.S. Preventive Services Task Force. Guide to Clinical Preventive Services. An Assess ment of the Effectiveness of 169 interventions: Report of the U.S. Preventive Services Task Force 1989;Baltimore: Williams & Wilkins.
6. Bates SE. Clinical applications of serum tumor markers. Ann of Int Med 1991;115:623-638.
7. Grimes DA, Schulz KF. Uses and abuses of screening tests. Lancet 2002;359:881-884.
8. Marshall KG. Prevention. How much harm? How much benefit? 4. The ethics of informed consent for preventive secreening programs Can Med Assoc J 1996;155:377-382.
9. Gates TJ. Screening for cancer: evaluating the evidence. Am Fam Physician 2001;63:513-522.