@article{JIS_2001__4_2_a6,
     author = {Grimm,  Uwe},
     title = {Improved bounds on the number of ternary square-free words},
     journal = {Journal of integer sequences},
     year = {2001},
     volume = {4},
     number = {2},
     zbl = {1004.05003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2001__4_2_a6/}
}