Tokyo, Sept. 20 (Jiji Press)--Japan's Sumitomo Mitsui Financial Group Inc. has said that it will additionally invest about 135 billion yen in Jefferies Financial Group Inc. of the United States. Sumitomo Mitsui's equity stake in Jefferies will rise to up to 20 pct from the current 14.5 pct. The two groups will also set up in Japan a joint venture to integrate their wholesale Japanese equi...