Safron, S. A.; Skofronick, J. G. & Winkle, D. H. Van. Investigations of the Dynamics and Growth of Surfaces and Ultra Thin Films by Helium Atom Scattering, report, September 27, 2006; (https://digital.library.unt.edu/ark:/67531/metadc873324/m1/1/: accessed January 16, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .