Pardi, Richard R.; Brickner, Dorene (1990). "Modern and Fossil Raindrop Impressions as a Lesson in Interpretation of Ancient Sedimentary Features". Journal of Geological Education. 38 (4): 316–317. doi:10.5408/0022-1368-38.4.316. ISSN0022-1368.
Pardi, Richard R.; Brickner, Dorene (1990). "Modern and Fossil Raindrop Impressions as a Lesson in Interpretation of Ancient Sedimentary Features". Journal of Geological Education. 38 (4): 316–317. doi:10.5408/0022-1368-38.4.316. ISSN0022-1368.