1. Graham Brown J. Medical Diagnosis: A manual of clinical method. 1st ed. London: Simpkin, Marshall; 1882. p66-67.
2. Ewing J. Clinical pathology of the blood; A treatise on the general principles and special applications of hematology. 1st ed. Philadelphia and New York: Lea Brothers; 1901. p38-46.
3. Graham Brown JJ, Ritchie WT. Medical diagnosis: A manual of clinical method for practitioners and students. 5th ed. Edinburgh & London: William Green & Sons; 1906. p96-101.
4. Abrams A. Manual of clinical diagnosis. Revised 2nd ed. San Francisco: S. Carson; 1892. p 95-96.