Xuan-Yong Zhu Wen-Feng Qi On the distinctness of modular reductions of maximal length sequences modulo odd prime powers. 1623-1637 2008 77 Math. Comput. 263 http://dx.doi.org/10.1090/S0025-5718-08-02075-9 db/journals/moc/moc77.html#ZhuQ08