Towards a heavy diquark effective theory for weak decays of doubly heavy baryons Yu-Ji Shi, Wei Wang, Zhen-Xing Zhao and Ulf-G. Meißner Eur. Phys. J. C, 80 5 (2020) 398 Published online: 11 May 2020 DOI: 10.1140/epjc/s10052-020-7949-z