[Washington, D.C.] : U.S. Dept. of the Interior, U.S. Geological Survey ; Denver, CO : Free on application to the U.S. Geological Survey, Information Services, [2000]
[Washington, D.C.] : U.S. Dept. of the Interior, U.S. Geological Survey ; Denver, CO : Free on application to the U.S. Geological Survey, Information Services, 1998