Gascon M, Cirach M, Martinez D, Dadvand P, Valentin A, Plasencia A, Nieuwenhuijsen MJ. Normalized difference vegetation index (NDVI) as a marker of surrounding greenness in epidemiological studies: the case of Barcelona city. Urban For Urban Green. 2016 Sep;19:88-94. doi: 10.1016/j.ufug.2016.07.001
Cohen LM, Britt DM, Collins FL, Stott HD, Carter LC. Chewing gum affects smoking topography. Exp Clin Psychopharmacol. 1999 Nov 1;7(4):444-7.