“…4. In addition, the anisotropy of shale strength has also been tested by a large number of researchers (Jaeger, 1960;Chenevert and Gatlin, 1965;Pinto, 1970;Jaeger, 1971;Vernik and Nur, 1992;Aoki et al, 1993;Ong, 1994;Vernik and Liu, 1997;Niandou et al, 1997;Willson et al, 1999Willson et al, , 2007Pei, 2008;Jaeger and Cook, 2009;Sondergeld and Rai, 2011;Kanitpanyacharoen et al, 2011;Wang et al, 2012;Li et al, Fig. 3.…”