Let X be a two-complex and G be its fundamental group. Let A be a non-trivial subgroup of G. The talk will describe a simple but delicate process for using A to define non-trivial elements of the second homotopy group of X. |

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Let X be a two-complex and G be its fundamental group. Let A be a non-trivial subgroup of G. The talk will describe a simple but delicate process for using A to define non-trivial elements of the second homotopy group of X. |