Neil Hindman, Dona Strauss. Some combinatorially defined subsets of beta N and their relation to the idempotents. Journal of Combinatorial Theory, Series A, 118(2):373-386, 2011. [doi]
@article{HindmanS11,
title = {Some combinatorially defined subsets of beta N and their relation to the idempotents},
author = {Neil Hindman and Dona Strauss},
year = {2011},
doi = {10.1016/j.jcta.2010.05.005},
url = {http://dx.doi.org/10.1016/j.jcta.2010.05.005},
researchr = {https://researchr.org/publication/HindmanS11},
cites = {0},
citedby = {0},
journal = {Journal of Combinatorial Theory, Series A},
volume = {118},
number = {2},
pages = {373-386},
}