Complex sentence: His eastern victories earned him his third triumph, which he celebrated on his 45th birthday in 61 BC, Pliny, Natural History, 37.6 seven months after his return to Italy.
Split into simpler sentences: His eastern victories earned him his third triumph. He celebrated it on his 45th birthday in 61 BC. Pliny, Natural History, 37.6 He waited for seven months after his return to Italy.