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• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeOct 8th 2012
• (edited Oct 8th 2012)

I have touched the formatting at free groupoid. Then I added the statement that the fundamental groups of a free groupoid are free. Also added a pointer to a writeup of the proof.

• CommentRowNumber2.
• CommentAuthorzskoda
• CommentTimeOct 9th 2012

Just unimportant question: is there an analogue of Fox derivative for free groupoids considered anywhere (Fox derivative is originally defined for group algebras of free groups) ?

• CommentRowNumber3.
• CommentAuthorTim_Porter
• CommentTimeOct 9th 2012

Yes. Ronnie, with Phil Higgins did something on those lines and I think it is in the triple authored book.

• CommentRowNumber4.
• CommentAuthorronniegpd
• CommentTimeJun 24th 2015
• (edited Jun 24th 2015)
The question concerns the relation between crossed complexes and chain complexes with a groupoid of operators which is fully discussed
in the book partially titled "Nonabelian Algebraic Topology". See Sections 7.4, 8.4, 9.5.
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