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@article{KRU72, author = {Kruskal, Joseph B.}, doi = {10.1016/0097-3165(72)90063-5}, journal = {Journal of Combinatorial Theory, Series A}, pages = {297--305}, sha256 = {0BC24CCB912E8753506C1B71534B06C2F6856F1B2C788F113EBC4A020ACE9A50}, title = {The theory of well-quasi-ordering: A frequently discovered concept}, volume = {13}, year = {1972} }