1. in Lehrbuch der Botanik, ed. , and , p. 699, G. Fischer Verlag, Stuttgart, New York (1978).
2. Chemotaxonomie der Pflanzen, Vol. 1, Birkhäuser Verlag, Basel, Stuttgart (1962).
3. and , Systematik des Pflanzenreichs, p. 95, G. Fischer Verlag, Stuttgart, New York (1985).
4. Secretory tissues in plants. Academic Press, London, New York, San Francisco (1979).
5. Resin ducts of Pinus halepensis Mill.-Their structure, development and pattern of arrangement