Complex sentence: In January 1901, Train became assistant in the office of the New York District Attorney and in 1904 he started his literary career with the publication of the short story "The Maximilian Diamond" in "Leslie's Monthly".
Split into simpler sentences: In January 1901, Train became assistant in the office of the New York District Attorney. In 1904 he started his literary career with the publication of the short story "The Maximilian Diamond" in "Leslie's Monthly".