| Study of fossil mammals in Hezheng China 2008-present. |
| Study of Samos stratigraphy, Greece, 1994-1996, 2002-2006. |
| Visiting scholar, Desert Lab, University of Arizona, Tucson, 1993. |
| Study of feeding in ruminants in Kenya, 1992. |
| Botanical study of tropical vegetation physiognomy in Kenya and Tanzania, 1992. |
| Geologic fieldwork on Samos, Greece, 1992. |
| Botanical study of tropical vegetation physiognomy in Venezuela and Puerto Rico, 1991. |
| Geologic fieldwork on Samos and Rhodes, Greece, 1990. |
| Geologic fieldwork and study of Miocene sediments and paleosols on Chios, Samos, Rhodes, Greece (with Jay Quade), 1989. |
| Collection of fossil mammals in the Siwalik deposits of Pakistan (with John Barry), 1987. |
| Study of stratigraphy on Samos, Greece, 1985. |
| Collection of radiometric samples on Samos, Greece (with Richard Hay and Robert Drake), 1982. |
| Study of stratigraphy and collection of pollen in lignites at Samos, Greece (with David Pilbeam), 1981. |
| Paleontological expedition, stratigraphic study, and prospecting for fossils on Samos, Greece, 1980. |
| Excavation and collection of rodents and stratigraphic study on Samos, Greece (with Craig Black, Leonard Krishtalka, Alan Kim, and Marc Weidmann), 1979. |
| Paleontological expedition of Paleocene sediments in Colorado (with Peter Robinson), 1979. |
| Paleontological expedition of Mesozoic sediments in Colorado (with Karl Hirsch), 1978. |
| Paleontological expedition of Eocene and Miocene sediments in Colorado (with Judith Harris and Peter Robinson), 1977. |
| Paleontological expedition in Tunisia (with Peter Robinson), 1976. |
| Rodent excavation and stratigraphic study on Samos, Greece (with Ken Carpenter, Judith Harris, Peter Robinson, John Van Couvering, Marc Weidmann), 1976. |
| Paleontological expedition of Mesozoic fossils in Colorado and South Dakota (with Judith Harris, Karl Hirsch, and Peter Robinson), 1976. |
| Paleontological expedition of Eocene fossils in Wyoming (with Judith Harris, Karl Hirsch, and Peter Robinson), 1975. |
| Paleontological expedition of Mesozoic fossils in Colorado and South Dakota (with Judith Harris, Karl Hirsch, and Peter Robinson), 1974. |
| Paleontological expedition on Maboko Island, Kenya (with Peter Andrews, Judith Harris, David Pilbeam, and John Van Couvering), 1973. |
| 2012-present Study of recent and fossil ungulates at the AMNH |
| 2012 Study fossil giraffes in Beijing and Hezheng China - Invited |
| 2012 Studied fossils in Uppsala Sweden and Munster and Frankfurt, Germany |
| 2011 Study of fossils in Basel and Lausanne, Switzerland |
| 2011 Study of fossils in the Geologic Museum and University of Lausanne, Switzerland |
| 2009 - Present - research in natural history museums in London (UK), Munich (Germany), New York, Harvard, Yale, University of Michigan, Athens Greece, Uppsala and Stockholm (Sweden), Bern, Basel, Lausanne (Switzerland), Beijing and Hezheng (China) |
| Research with equids and camelids at the AMNH 2005-2009 |
| Research with Miocene bovids from Pakistan at Harvard 2000-2009 |
| Paleontological Institute Munich, 2005 |
| Fossils from Greece and Pakistan, at AMNH, New York, 2001-2004 |
| Fossils from Pakistan, Peabody Museum, Harvard, Cambridge, 2004 |
| National Museum of Natural History, Paris - The Natural History Museum, London, 1999-2000 |
| Senckenberg Natural History Museum, Frankfurt, 1999-2002 |
| Paleontological Institute Munich, 2001-2001 |
| Study fossils in Finland, Greece, Sweden, UK, Germany, France, and Switzerland, 1996-1999 |
| Giraffes and antelopes, American Museum of Natural History and Peabody Museum -Harvard, 1994-1999. |
| Fossils from Kenya, Berkeley California, 1993, 1994, 1995. |
| Fossils from Sinap, Turkey in Helsinki, Finland, 1993. |
| Fossils from Shanxi, China in Uppsala, Sweden, 1993 and 1999. |
| Fossils from Pikermi in Stockholm, Sweden, 1993 and 1999. |
| Fossils from Kenya, study of giraffids at National Museums of Kenya (NMK), Nairobi, 1992. |
| Fossils from Greece and Pakistan, at Peabody Museum (PM), Cambridge and American Museum of Natural History (AMNH), New York, 1989-1993. |
| Fossils from France, Greece, and Pakistan, giraffids and bovids, at British Museum of Natural History (NHM), London, 1992. |
| Fossils from USA, Greece, and Pakistan, at AMNH, New York, 1988. |
| Fossils from France, Kenya, and Greece, hyaenids, giraffids and bovids at National Museum of Natural History (NMHNP), Paris, Seckenberg Museum of Natural History (SMF), Frankfurt, and NMK, Nairobi, 1987. |
| Fossils from France, Greece, and Pakistan, hyaenids, giraffids, and bovids in Paleontological Institute (PIW) and Natural History Museum (NHMW), Vienna, MNHNP, Paris, Natural History Museum (NHMBa), Basel, Geological Museum (MGL), Lausanne, Natural History Museum (SNHMS), Stuttgart, Paleontological and Geological Institute (PIM), Munster, and NHM, London 1986. |
| Fossils from USA, Greece, and Pakistan, at AMNH, New York, 1982. |
| Fossils from France, Greece, and Pakistan, at NHM, London, MGL, Lausanne, and Natural History Museum (MHNG), Geneva, 1981. |
| Fossils from the Siwalik deposits of Pakistan, at Geological Survey (GSP), Pakistan, 1981. |
| Fossils from Greece and Pakistan, at AMNH, New York, 1980. |
| Fossils from the Siwalik collections, at Yale Peabody Museum (YPM), New Haven, 1980. |
| Fossils from Greece, at Carnegie Museum of Natural History (CM), Pittsburgh, 1979. |
| Fossils from Greece and Pakistan, at AMNH, New York, 1978 and 1979. |
| Fossils from Greece and China, at University of Padova Museum (UPM), Padova, NHMBa, Basel, Natural History Museum (NHMBe) Bern, SNHMS, Stuttgart (Ludwigsburg), Natural History Museum (NHMD), Darmstadt, Natural History Museum (NHMT), Tubingen, MNHNP, Paris, 1977. |
| Cataloguing, classifying, preparing, and organizing the Samos Munster collection, 1977. |
| Fossils from France, Greece, and Pakistan, at AMNH, New York, CM, Pittsburgh, YPM, New Haven, and PM, Cambridge, 1976. |
| Fossils from Greece, at PIW and NHMW, Vienna, Paleontological Institute (PIM), Munich, SNHMS, Stuttgart (Ludwigsburg), PIM, Munster, SMF, Frankfurt, MGL, Lausanne, MNHNP, Paris, NHM, London, 1975. |
| Cataloguing, classifying, preparing, and organizing the North American Miocene and Tunisian collections, at the University of Colorado Museum (UCM), 1974 - 1977. |