Complex sentence: Perelman was officially awarded the Millennium Prize on March 18,2010, but he also declined the award and the associated prize money from the Clay Mathematics because the Interfax news agency quoted Perelman as saying he believed the prize was unfair.
Split into simpler sentences: Perelman was officially awarded the Millennium Prize on March 18,2010, but he also declined the award and the associated prize money from the Clay Mathematics. The Interfax news agency quoted Perelman as saying he believed the prize was unfair.