Ringel–Kotzig decomposition conjecture

Let $n\geq 1$, and let $K_{2n+1}$ be the complete graph on $2n+1$ vertices. Ringel–Kotzig decomposition conjecture. The graph $K_{2n+1}$ can be decomposed into $2n+1$ subgraphs, all isomorphic to a given tree with $n$ edges. This is a tree-decomposition problem closely connected with graceful labelings. The supplied source presents it as a longstanding conjecture and gives no resolution evidence.