Round 4 of the Teplice Open A-group kicks off Tuesday in the Czech Republic. The nine-round Swiss continues to sort out contenders in what looks like a competitive field. Players get 90 minutes for 40 moves, then 30 minutes to finish, with 30 seconds added per move. The format rewards preparation and endurance in equal measure. Watch for rating swings as mid-table players jockey for position heading into the back half.