Complex sentence: His first published work was "Kronski/McSmash" which he wrote around the age of 20 and had it published in 1969 in the United Kingdom and 1970 in the United States.
Split into simpler sentences: His first published work was "Kronski/McSmash" which he wrote around the age of 20. It was published in 1969 in the United Kingdom and 1970 in the United States.