W. Duke: Continued fractions and modular functions. Bull. AMS ... (2005), ... 11565 Cristian Gonzalez: Class numbers of quadratic function fields and continued fractions. J. Number Theory 40 (1992), 38-59. Peter Ho''pner: Perioden halbregelma''s''iger Kettenbru''che und Idealperioden in reell-quadratischen Ordnungen. Grazer Math. Ber. 331 (1997), 93p. 1974 R. Mollin/H. Williams: Continued fractions of period five and real quadratic fields of class number one. Acta Arithmetica 56 (1990), 55-63. [3323]