US Geological Survey, MS 973, Denver, CO 80225, USA;
US Geological Survey, MS 9541 Reston, VA 20192, USA;
US Geological Survey, 2280 Woodale Drive, St. Paul, MN 55112, USA;
Servicio Geologico Mexicano, 78280 San Luis Potosl, S. L. P. , Mexrico;
Geological Survey of Canada, Natural Resources Canada, 601 Booth St. , Ottawa, ON, Canada, K IA OE8;
Geological Survey of Canada, Natural Resources Canada, 601 Booth St. , Ottawa, ON, Canada, K IA OE8;