On the maximal solvable subgroups of semisimple algebraic groups
  Let $G$ be a semisimple affine algebraic group defined over a field $k$ of characteristic zero. We describe all the maximal connected solvable subgroups of $G$, defined over $k$, up to conjugation by rational points of $G$. 
Hassan Azad, Indranil Biswas and Pralay Chatterjee
math.GR math.AG