1. W. A. D. Anderson, and W. A. D. Anderson (1966 ) Pathology , 5th edition . Volume 1 . Mosby, St. Louis, p.67 .
2. Postmaturity
3. D. F. Cappell (1964 ) Muir's Textbook of Pathology , 8th edition , Arnold, London, p.116 .
4. CALCIFICATION OF THE PLACENTA
5. Placental calcification and seasonal difference