Balanced Partitions of Vector Sequences
  Let $d, r \in \N$, $\|\cdot\|$ any norm on $\R^d$ and $B$ denote the unit ball with respect to this norm. We show that any sequence $v_1,v_2,...$ of vectors in $B$ can be partitioned into $r$ subsequences $V_1, ..., V_r$ in a balanced manner with respect to the partial sums: For all $n \in \N$, $\ell \le r$, we have $\|\sum_{i \le k, v_i \in V_\ell} v_i - \tfrac 1r \sum_{i \le k} v_i\| \le 2.0005 d$. A similar bound holds for partitioning sequences of vector sets. Both results extend an earlier one of B\'ar\'any and Grinberg (1981) to partitions in arbitrarily many classes. 
Imre B\'ar\'any and Benjamin Doerr