1. Atlas of Israel, 1956, Jerusalem: The Jewish Agency.
2. Baker, H. G., Baker, I., 1973: Some anthecological aspects of the evolution of nectarproducing flowers, particularly amino acid production in nectar. InHeywood, V. H. (Ed.): Taxonomy and Evolution, pp. 243?264. ? London: Academic Press.
3. ?, 1983: Insects as flower visitors and pollinators. ? Ann. Rev. Entomol.28, 407?453.
4. Baker, I., Baker, H. G., 1982: Some chemical constituents of floral nectars ofErythrina in relation to pollinators and systematics. ? Allertonia3, 25?38.
5. Corbet, S. A., 1978: Bees and nectar ofEchium vulgare. ? InRichards, A. J., (Ed.): The Pollination of Flowers by Insects, pp. 21?30. ? New York: Academic Press.