1. Images and quotients of SO3R: remarks on a theorem of Van der Waerden;Comfort;Rocky Mountain J. Math.,1987
2. F. Hausdorff, Grundzuge der Mengenlehre, Leipzig: Veit, 1914, Reprinted, Chelsea, New York
3. Free subgroups in SO3Q;Liu;Comm. Algebra,1999
4. Problem 6102;Osofsky;Amer. Math. Monthly,1976
5. Problem 6102 and solution;Osofsky;Amer. Math. Monthly,1978