Andrea Cassa: Dinamiche caotiche e misure invarianti. Tesi Firenze 1995. Stefano Marmi/Pierre Moussa/J. Yoccoz: The Brjuno functions and their regularity properties. Comm. Math. Phys. 186 (1997), 265-293. 11558 Pierre Moussa/Andrea Cassa/Stefano Marmi: Continued fractions and Brjuno functions. Univ. Firenze, rapporto 1997/26 (1997), 12p. 21213 Manuel Stadlbauer: Metrische Zahlentheorie und dynamische Systeme. Internet 2006, 63p. J. Yoccoz: Theoreme de Siegel, polynomes quadratiques, et nombres de Brjuno. Asterisque 231 (1995), 3-88.