The Circuit Double Cover Conjecture of Szekeres and Seymour

Let $G$ be a 2-edge-connected graph, and let a circuit double cover be a family of circuits in which every edge of $G$ is covered twice. Circuit Double Cover Conjecture. Every 2-edge-connected graph has a family of circuits which covers every edge twice.

This is a longstanding conjecture in graph theory. The source states that the Shortest Circuit Cover Conjecture implies it, and that by Fleischner's splitting lemma it suffices to establish it for 2-edge-connected cubic graphs.