1. Esau, K. (1964).Plant Anatomy.John Wiley & Sons, New York. USA. 539–542.
2. Jensen, W. A. (1962).Botanical Histochemistry.W.H. Freeman and Company, San Francisco, CA, USA. 55–99.
3. Maniatis, T., Fritsch, E. F. and Sambrook, J. (1989).Molecular Cloning: A Laboratory Manual.Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, USA. 7.46–7.50, 9.34–9.35, 9.38–9.46.