Complex sentence: In 1963 the first "Dandy" summer special was published, a joint "Dandy-Beano summer special", the first exclusively "Dandy Summer Special" was released the following year.
Split into simpler sentences: In 1963 the first "Dandy" summer special was published. This was a joint Dandy-Beano summer special, the first Dandy Summer Special on its own being released the following year.