The error in the OP is a typo that could never seriously confuse anyone, as the element Gr does not exist. An interesting perspective is Terry Tao's on local v

The error in the OP is a typo that could never seriously confuse anyone, as the element Gr does not exist. An interesting perspective is Terry Tao's on local vs. global errors (https://terrytao.wordpress.com/advice-on-writing-papers/on-local-and-global-errors-in-mathematical-papers-and-how-to-detect-them/ https://terrytao.wordpress.com/advice-on-writing-papers/on-l...). A typo like this, even if propagated, is a local error which at worst makes it very annoying to Ctrl-F papers or do literature review. Local errors deserve to be corrected, but in practice their importance to science as a field is small.