Big fundamental groups

Cannon and Conner, in a three-paper series ([۱], [۲], and [۳) developed the notion of “ Big fundamental group”, whose construction ismotivated by and similar to that of the (classical) fundamental group. In fact, it coincides with the fundamental group in the case ofsecond-countable spaces. “ Big fundamental groups” is a powerful tool that can be used for distinguishing spaces that are notdistinguishable using the fundamental group.