Ahmet Tekcan and  Arzu Özkoç,  Quadratic Irrationals, Quadratic Ideals and Indefinite Quadratic Forms II.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    November 2009, vol. 35(11). 1063 - 1066
    [viewed 21 January 2020]. Available from: https://publications.waset.org/pdf/2294.