1. Permian system of Colorado Plateau;Baars;AAPG Bull.,1962
2. Permian chronostratigraphy in Kansas;Baars;Geology,1990
3. Navajo Country: A Geology and Natural History of the Four Corners Region;Baars,1995
4. Redefinition of the Pennsylvanian-Permian boundary in Kansas, mid-continent USA;Baars;Int. Geol. Rev.,1992
5. Correlation of the Permian of southern Utah, northern Arizona, northwestern New Mexico, and southwestern Colorado;Baker;AAPG Bull.,1929