Complex sentence: In the past 25 years a number of research groups throughout the world have continued the early groundbreaking work of Sweet and Fairchild, and in particular, the pioneering clinical studies of Hiroshi Hatanaka in Japan.
Split into simpler sentences: In the past 25 years a number of research groups throughout the world have continued the early groundbreaking work of Sweet and Fairchild. In particular, the pioneering clinical studies of Hiroshi Hatanaka in Japan.