How widespread is electronic cigarette use in outdoor settings? A field check from the TackSHS project in 11 European countries. - Amalia, Beladenta; Rodríguez, Alejandro; Henderson, Elisabet; Fu, Marcela; Continente, Xavier; Tigova, Olena; Semple, Sean; Clancy, Luke; Gallus, Silvano; Fernández, Esteve; López, Maria J. (Environmental Research, 2021)