“…Other sources used are extra contents sent within the main content [10, 17, 28-32, 34, 41, 44, 46, 48, 53, 55, 57, 60, 61, 64, 70, 83]; extra contents provided by the broadcaster's web servers (interactive channel) [24,33,39,45,47,58,63,66,67]; extra content provided by web servers indicated by the broadcaster [18,35,37,43,51,58,65,69]; independent extra content providers [39,62,64,67,68,82]; and extra content generate in the client side: contextual information [19,20,38,54,65,77,84] and user generated information [23-25, 36, 42, 76, 79]. Contextual information uses information related to the user and collected from his environment, such as geolocalization, and social networks profiles.…”