Complex sentence: Ectoplasm is said to be associated with the formation of spirits; however since World War II reports of ectoplasmic phenomena have declined and many parapsychologists doubt whether genuine cases ever existed.
Split into simpler sentences: Ectoplasm is said to be associated with the formation of spirits. However, since World War II, reports of ectoplasmic phenomena have declined and many parapsychologists doubt whether genuine cases ever existed.