@article{SIGMA_2015_11_a48,
     author = {Kyungyong Lee and Li Li and Matthew R. Mills},
     title = {A {Combinatorial} {Formula} for {Certain} {Elements} of {Upper} {Cluster} {Algebras}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2015},
     volume = {11},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2015_11_a48/}
}