All in one string quartets 12 + 13 + 14 - Gudmundsen-Holmgreen, Pelle 1932-2016 (Hansen, 2013)
For 3 string quartets (6 violins, 3 violas, 3 cellos). - "The quartets 12 and 13 and 14 can be performed WITHOUT the extra instruments (ad libitum). String quartet 12: Each in each, String quartet 13: Mutual ordering, String quartet 14: Well-tuned sounds. String quartets 12 + 13: True concord I, String quartets 12 + 14: True concord II, String quartets 13 + 14: True concord III. String quartets 12 + 13 + 14: All in one"--Page 105. - Cover title