@article{Strassmann2011,
author = {Strassmann, B.I. },
title= {Cooperation and competition in a cliff-dwelling people},
year = {2011},
doi = {10.1073/pnas.1100306108},
journal = {Proceedings of the National Academy of Sciences },
volume = {108},
number = {Suppl. 2},
pages = {10894--10901},
}