@article{GDZPPN002478153,
title = {The Length of Periodic Continued Fractions.},
journal = {Monatshefte f\"ur Mathematik},
volume = {76},
year = {1972},
pages = {428-435},
zbl = {0245.10005},
url = {http://dml.mathdoc.fr/item/GDZPPN002478153}
}
Hirst, K.E. The Length of Periodic Continued Fractions.. Monatshefte für Mathematik, Tome 76 (1972) pp. 428-435. http://gdmltest.u-ga.fr/item/GDZPPN002478153/