“…A number of studies have been conducted that evaluate the effectiveness and efficiency of search engines (Ali and Beg, 2011; Ali and Gul, 2016; Bar-Ilan, 2002, 2007; Bilal, 2012; Brin and Page, 1998; Buckley and Voorhees, 2000; Can et al , 2004; Chu and Rosenthal, 1996; Deka and Lahkar, 2010; Ding and Marchionini, 1996; Dresel et al , 2001; Garoufallou, 2012; Garoufallou et al , 2008; Goh and Ang, 2003; Gordon and Pathak, 1999; Griesbaum, 2004; Griesbaum et al , 2002; Guggenheim and Bar-Ilan, 2005; Hawking and Craswell, 2005; Kaur, et al , 2011; Kerkmann and Lewandowski, 2012; Kumar and Prakash, 2009; Landoni and Bell, 2000; Lazarinis, 2007; Leighton and Srivastava, 1999; Lewandowski, 2006, 2008a; 2008b; 2011, 2015; Li and Shang, 2000; Macfarlane, 2007; Mahmoudi, et al , 2014; Martínez-Sanahuja and Sánchez, 2016; Oppenheim, et al , 2000; Sadeghi, 2011; Shang and Li, 2002; Stock and Stock, 2000; Tung-Tam, 2004; Usmani, et al , 2012; Vassilakaki et al , 2015; Vaughan, 2004; Ve´ronis, 2006 as cited in Lewandowski, 2015; Yu and Kaufman, 2007; Zhang and Fei, 2010; Zhang, et al , 2013).…”