(29 references below)

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• UBAGHS, J. C.  1879.  Description Géologique et Paléontologique du Sol de Limbourg.  Roermond:  Romen & Fils, 1–275.
• UDDEN, J. A.  1907.  A Sketch of the Geology of the Chisos Country, Brewster County, Texas.  University of Texas Bulletin 93 (Science Serial 11).
• UDDEN, J. A.  1908.  A Cycad From the Upper Cretaceous in Maverick County, Texas.  Science, New series 28, 159–160.
• UDDEN, J. A.; Baker, C. L.; Böse, E.  1919.  Review of the Geology of Texas.  University of Texas Bulletin 44.
• UHLENBROEK, G. D.  1912.  Het Krijt van Zuid-Limburg. Toelichting Bij Eene Geologische Kaart van het Krijt-Gebied van Zuid-Limburg.  Jversl. Rijksopsp. Delfstoffen over 1911, 48–57.
• UHLIG, V.  1883.  Der Cephalopoden der Wernsdorfer Schichten.  Denkschrift Akademie Wissenschaft, Wien 46 (2), 127-290.
• UHLIG, V.  1894.  Bemerkungen zur Gliederung Karpatischer Bildungen.  Jb. K.-K. Geol. Reichsanst. 44, 215–222.
• UHLIG, V.  1907.  Review of Cragin, F. W., Paleontology of the Malone Jurassic Formation of Texas.  Neues Jahrbuch 1, 285–286.
• ULRICH, E. O.  1904.  Fossils and Age of the Yakutat Formation [Alaska].  Harriman Alaska Expedition 4, 125-146.
• UMBERGER, J.; Umberger, A. L.  1967.  Texas Mineral and Fossil Locations.  Tyler:  Tyler Star Publishing.
• UMBGROVE, J. H. F.  1925.  De Anthozoa uit het Maastrichtsche Tufkrijt.  Leidsche Geol. Meededel. 1, 83–126.
• UMBGROVE, J. H. F.  1926.  Bijdrage tot de Kennis der Stratigraphie, Tektonik en Petrographie van het Senoon in Zuid-Limburg.  Leidsche Geol. Meededel. 1, 255–332.
• UNDERWOOD, J. R., Jr.  1961.  Geology of the Eagle and Indio Mountains, Trans-Pecos, Texas.  PhD Thesis, University of Texas, Austin.
• UNDERWOOD, J. R., Jr.  1963.  Geology of Eagle Mountains and Vicinity, Hudspeth County Texas, Texas.  Bureau of Economic Geology, University of Texas Quadrangle Map 26.  
• UNDERWOOD, J. R., Jr.  1980.  Geology of the Eagle Mountains, Hudspeth County, Texas.  New Mexico Geological Society Guidebook, Trans-Pecos Region, Southeastern New Mexico and West Texas, 31st Field Conference, 183-194.
• UNITED STATES CORPS OF ENGINEERS-PHILADELPHIA DIST.  1967.  Inland Waterway-Delaware River to Chesapeake Bay-Historic Chesapeake & Delaware Canal.  Philadelphia:  United States Government Printing Office, 1–16.
• UNITED STATES CORPS OF ENGINEERS-PHILADELPHIA DIST.  1972.  Helpful Hints for Fossil Collecting in Chesapeake & Delaware Canal.  Philadelphia:  United States Government Printing Office, 1–4.
• UNITED STATES CORPS OF ENGINEERS-PHILADELPHIA DIST.  1974.  The Chesapeake & Delaware Canal.  Philadelphia:  United States Government Printing Office, 1–16.
• UNITED STATES CORPS OF ENGINEERS-PHILADELPHIA DIST.  1979.  The Chesapeake & Delaware Canal.  Philadelphia:  United States Government Printing Office, 1-2.
• UPHAM, W.  1888.  "The Geology of Crow Wing and Morrison Counties".  In:  Winchell, N. H.  The Geology of Minnesota, Vol. 2 of the Final Report.  Geological and Natural Survey of Minnesota, 580–611.
• UPCHURCH, G. R.; Crane, P. R.; Drinnan, A. N.  1994.  The Megaflora from the Quantico Locality (Upper Albian), Lower Cretaceous Potomac Group of Virginia.  Virginia Museum of Natural History Memoir 4, 1–64.
• URBANI, F.; Yoris, F.; Renz, O.  1989.  Nota Sobre un Amonite del Genero Mariella, San Agustin, Caripe, Estado Monagas.  Geos 20, 91−96.
• URBANI, F.; Yoris, F.; Szcerban, E.; Renz, O.; Jung, P.  1989.  Una Localidad Fosilifera en la Fase Tacagua, Cordillera de la Costa.  Geos 29, 274−275.
• URMANOVA, S. K.  1962.  On a Species of Ammonite from the Lower Cretaceous Deposits of Badkhyz, Turkmenia, U.S.S.R.  Paleont. Zhurnal 2, 76–79.
• URMANOVA, S. K.; Tashlev, M. S.  1967.  Albskie Otlozhenija Centralnogo, Gjaurskogo, Vostochnogo Kopet-Daga i Gornogo Badkhyza.  Izv. AN TSSR, Ser. Fiz.-Tekn., Khim. i Geol. Nauk 5, 117–124.
• URRETTE, M. B. A.  1986.  Aptian Ammonites from the Argentinian Austral Basin.  The Subfamily Helicancylinae Hyatt, 1894.  Annals of the South African Museum 96 (6), 271–314.
• URRETTE, M. B. A.; Klinger, H. C.  1986.  Upper Barremian Heteroceratinae (Cephalopoda, Ammonoidea) from Patagonia and Zululand, with Comments on the Systematics of the Subfamily.  Annals of the South African Museum 96 (8), 315–358.
• USHER, J. L.  1952.  Ammonite Faunas of the Upper Cretaceous Rocks of Vancouver Island, British Columbia.  Canada Geological Survey Bulletin 21, 1–182.