arXiv · math/0702504
Let $H$ be a character Hopf algebra. Every right coideal subalgebra that contains the coradical has a PBW-basis which can be extended up to a PBW-basis of $H.$
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V. K. Kharchenko. 2007-02-17. On right coideal subalgebras. https://arxiv.org/abs/math/0702504
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