Koh et al. (1980) showed that -tadpole graphs are graceful
1, or 3 (mod 4) and conjectured that all tadpole graphs are graceful
(Gallian 2018). Guo (1994) apparently completed the proof by filling in the missing
case in the process of showing that tadpoles are graceful when or 2 (mod 4) (Gallian 2018).
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S.-R. and Park, J. Y. "On Super Edge-Magic Graphs." Ars Combin.81,
113-127, 2006.Koh, K. M.; Rogers, D. G.; Teo, H. K.;
and Yap, K. Y. "Graceful Graphs: Some Further Results and Problems."
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