@article{EJC_1996__3_1_118904,
     author = {Squire, Matthew B.},
     title = {Gray codes for -free strings.},
     journal = {The Electronic Journal of Combinatorics [electronic only]},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {1996},
     zbl = {0849.94021},
     language = {en},
     url = {https://geodesic-test.mathdoc.fr/item/EJC_1996__3_1_118904/}
}