Complex sentence: The mainline Presbyterian denominations as well as the Reformed are returning once again to their deep liturgical roots, since he Presbyterians were a direct separation from the Roman Catholic Church thru John Calvin in France/Switzerland and John Knox in Scotland.
Split into simpler sentences: The mainline Presbyterian denominations as well as the Reformed are returning once again to their deep liturgical roots. Since the Presbyterians were a direct separation from the Roman Catholic Church thru John Calvin in France/Switzerland and John Knox in Scotland.