Free Download Discontinuous groups and automorphic functions… By Joseph Lehner Publisher American Mathematical Society 1964 ISBN 0-8218-1508-3,978-0-8218-1508-3,83-1877-265-2,62-1940-233-2,39-1936-299-3,97-1960-225-2,127-1954-33-8,39-1938-433-4,62-1940-127-1..