Explicit coproduct formula for quantum groups of infinite series
  We find an explicit form for the coproduct formula for PBW generators of quantum groups of infinite series $U_q(\frak{sp}_{2n})$ and $U_q(\frak{so}_{2n}).$ Similar formulas for $U_q(\frak{sl}_{n+1})$ and $U_q(\frak{so}_{2n+1})$ are already known. 
Vladislav Kharchenko
math.QA