; Freeman, J. H. 878. The sulphates and selenate of polonium. Journal of the Chemical Society (Resumed). 1956: 4579. ISSN 0368-1769. doi:10.1039/jr9560004579
Deaver, Jr., B. S.; Everitt, C. F.; Micelson, P. F. (编). Near Zero: New Frontiers of Physics. New York: W. H. Freeman and Company(英语:W. H. Freeman and Company)
两栖动物分类表 Carroll, Robert L. Vertebrate Paleontology and Evolution. W. H. Freeman. 1988. ISBN 978-0-7167-1822-2. Carroll, Robert L. The Rise of Amphibians: