big fundamental groups

Cannon and conner, in a three-paper series ([1], [2], and [3) developed the notion of “ big fundamental group”, whose construction is motivated by and similar to that of the (classical) fundamental group. in fact, it coincides with the fundamental group in the case of second-countable spaces. “ big fundamental groups” is a powerful tool that can be used for distinguishing spaces that are notdistinguishable using the fundamental group.