The Edge-graceful Spectra of Connected Bicyclic Graphs Without Pendant

Let \( G \) be a connected simple \( (p, q) \)-graph and \( k \) a non-negative integer. The graph \( G \) is said to be \( k \)-edge-graceful if the edges can be labeled with \( k, k+1, \dots, k+q-1 \) so that the vertex sums are distinct modulo \( p \). The set of all \( k \) where \( G \) is \( k \)-edge-graceful is called the edge-graceful spectrum of \( G \). In 2004, Lee, Cheng, and Wang analyzed the edge-graceful spectra of certain connected bicyclic graphs, leaving some cases as open problems. Here, we determine the edge-graceful spectra of all connected bicyclic graphs without pendant.