Embeddings of Lipschitz-free spaces into ℓ1

We show that, for a separable and complete metric space $M$, the Lipschitz-free $\mathcal F(M)$ embeds linearly almost-isometrically into $\ell_1$ if only $M$ is subset of an $\mathbb R$-tree with length measure 0. Moreover, it isometrically closure set branching points (taken in any minimal that contains $M$) negligible. also prove R$-tree, every extreme point unit ball element form $(\delta(x)-\delta(y))/d(x,y)$ $x\neq y\in M$.