[1] NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA
[2] NYU, DEPT PHYS, NEW YORK, NY 10003 USA
[3] CALTECH, PALOMAR OBSERV, DIV PHYS MATH & ASTRON, PASADENA, CA 91125 USA
[4] UNIV FLORIDA, ROSEMARY HILL OBSERV, DEPT ASTRON, GAINESVILLE, FL 32611 USA
[5] UNIV MICHIGAN, RADIO ASTRON OBSERV, DEPT ASTRON, ANN ARBOR, MI 48109 USA
[6] UNIV MASSACHUSETTS, DEPT PHYS & ASTRON, AMHERST, MA 01003 USA
[7] UNIV ARIZONA, STEWARD OBSERV, TUCSON, AZ 85721 USA
[8] UNIV TEXAS, DEPT ASTRON, AUSTIN, TX 78712 USA
[9] COLUMBIA UNIV, COLUMBIA ASTROPHYS LAB, NEW YORK, NY 10027 USA
[10] UNIV WYOMING, DEPT PHYS & ASTRON, LARAMIE, WY 82071 USA
[11] WILLIAMS COLL, DEPT PHYS & ASTRON, WILLIAMSTOWN, MA 01267 USA
[12] NATL RADIO ASTRON OBSERV, CHARLOTTESVILLE, VA 22901 USA
[13] APPALACHIAN STATE UNIV, BOONE, NC 28608 USA