Cohen N.; Kov�e M.2025-02-1720202http://dx.doi.org/10.1016/j.disc.2020.112031https://idr.iitbbs.ac.in/handle/2008/2739It is shown that the graph obtained by merging two vertices of two 4-cycles is not a ?-graceful partial cube, thus answering in the negative a question by Bre�ar and Klav�ar from Bre�ar and Klav�ar (2006), who asked whether every partial cube is ?-graceful. � 2020 Elsevier B.V.Graceful labelings; Partial cubes; Ringel�Kotzig conjecture; TreesArticle