Ok. I found this tiny quote referring to two publications:
Methods of propagation are discussed in detail in the literature [20,22].
20. Horton, Jerome S. 1949. Trees and shrubs for erosion control of southern
California mountains. Berkeley, CA: U.S. Department of Agriculture,
Forest Service, California [Pacific Southwest] Forest and Range
Experiment Station; California Department of Natural Resources, Division
of Forestry. 72 p. [10689]
22. Hyland, Bob. 1990. Fremontodendron `California glory'. Public Garden.
Wayne, PA: Journal of the American Association of Botanical Gardens and
Arbors; 6(2): 41-42. [21985]
the second one is a journal and may be found perhaps at the library at your university.
