@article{10_37236_3035,
     author = {Samuel A Alexander},
     title = {Biologically unavoidable sequences},
     journal = {The electronic journal of combinatorics},
     year = {2013},
     volume = {20},
     number = {1},
     doi = {10.37236/3035},
     zbl = {1266.05105},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/3035/}
}