Complex sentence: In 1981, Veltman left Utrecht University for the University of Michigan-Ann Arbor, frustrated by the recognition his student Gerardus' t Hooft got for his PhD thesis on the renormalization of Yang-Mills theory.
Split into simpler sentences: In 1981, Veltman left Utrecht University for the University of Michigan-Ann Arbor. He was frustrated by the recognition his student Gerardus' t Hooft got for his PhD thesis on the renormalization of Yang-Mills theory.