11. The voiced labial fricative " v " varies ( idiolectal free variation ) between labiodental and bilabial. 12. The Fruit & No-Nut Bar is a nut-free variation of the popular fruit and nut energy bar. 13. Copper-free variations to the Sonogashira reaction have been developed to avoid the formation of the homocoupling products. 14. Both sounds, however, are in free variation . 15. The initial /'/ may be pronounced as either [ ? ] or [ ? ] in free variation . 16. In Wolof, a back-released velar click is in free variation with a lateral click or an alveolar click. 17. It's a free variation phonological alternation. 18. In other positions, etymological seems to be in free variation with ( etymological, however varies only with ). 19. Before [ i ] it is optionally palatalized [ dz ] in free variation with [ dz ]. 20. As with its constituent vowels, diphthongs with short and are subject to the same free variation described above.