First experimental constraint of the spectroscopic amplitudes for the alpha-cluster in the B-11 ground state, Y.P. Shen, B. Guo, T.L. Ma, D.Y. Pang, D.D. Ni, Z.Z. Ren, Y.J. Li, Z.D. An, J. Su, J.C. Liu, Q.W. Fan, Z.Y. Han, X.Y. Li, Z.H. Li, G. Lian, Y. Su, Y.B. Wang, S.Q. Yan, S. Zeng, W.P. Liu, Phys. Lett. B 797, 134820 (2019)