Complex sentence: To account for these apparent discrepancies, Paul Cornell proposed the "Season 6B" theory, first published in the 1995 book "The Discontinuity Guide", by Cornell, Martin Day and Keith Topping.
Split into simpler sentences: To account for these apparent discrepancies, the "Season 6B" theory was proposed. It was first published in the 1995 book "The Discontinuity Guide", by Paul Cornell, Martin Day and Keith Topping.