“…Considering the set of research papers included in the analysis, we observed the first approach of NN techniques to the stock market dates to the year 1991 (Trippi & Desieno, 1991). The range of applications of NNs in the stock market includes the prediction of stock market indices (Das & Uddin, 2013; Nayak et al, 2014; Ou & Wang, 2009), prediction of future signs of stock market returns (Lahmiri, 2011), prediction of stock price (Arasu et al, 2014; Hargreaves & Hao, 2013; Hsieh et al, 2011; Kim & Han, 2000), prediction of abnormal stock market returns (Safer, 2003), financial time‐series forecasting (Chen et al, 2006; Shaikh & Chhajed, 2012), stock market trading (Vanstone et al, 2010), and uncovering the predictive relationships of numerous financial and economic variables (Thawornwong & Enke, 2004). Macroeconomic variables, external events, twitter sentiments, and financial news, for instance, affecting stock markets are considered external factors.…”