Complex sentence: Teams were paired across the 13 rounds of competition according to the Swiss system (due to late start of the Olympiad the last round was cancelled); the open division was played over four boards per round, whilst the women's was played over three.
Split into simpler sentences: Teams were paired across the 13 rounds of competition according to the Swiss system. The open division was played over four boards per round, whilst the women's was played over three.