8944605 402291177618fa28bc965d80ad2ea49e juanmarqz http://gravatar.com/juanmarqz juanmarqz http://0.gravatar.com/avatar/402291177618fa28bc965d80ad2ea49e http://0.gravatar.com/avatar/402291177618fa28bc965d80ad2ea49e thumbnail juanmarqz periodic N_k-bundles over the 1-sphere, groupoids, sum of recoprocals