Complex sentence: It was Ippen who asserted that Skanderbeg was burried in the castle of Lezhë based on the work of Barletius who wrote that Skanderbeg was buried in the Church of St. Nicholas, without explanation if the church's building was inside or outside the castle.
Split into simpler sentences: It was Ippen who asserted that Skanderbeg was burried in the castle of Lezhë. His opinion was based on the work of Barletius who wrote that Skanderbeg was buried in the Church of St. Nicholas, without explanation if the church's building was inside or outside the castle.