“…Feature extraction and feature selection were identified as main objectives in four different studies (4/16, 25%) [48,50,53,56]. The remaining categories (Entity Recognition, Theme Identification and Emotion Recognition) were identified only in a study (1/16, 6.25%) [47,49,55]. In total, 4 of 16 studies (25%) can be grouped in two categories, involving text classification (3/4) [47,48,53] or score estimation (1/4) [56].…”