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Chris Ryan. Under Cover (Agent 21) [Internet]. Red Fox; 26AD. Available from: http://www.amazon.co.uk/Under-Cover-Agent-Chris-Ryan/dp/1849410119/ref=pd_bxgy_14_img_2?ie=UTF8&refRID=0RP05ACPVVVTGK2MGFAT
2.
Chris Ryan. Deadfall: Agent 21 [Internet]. Red Fox; 10AD. Available from: http://www.amazon.co.uk/gp/product/1849410100/ref=s9_simh_gw_p14_d12_i3?pf_rd_m=A3P5ROKL5A1OLE&pf_rd_s=desktop-1&pf_rd_r=15EF7PMZHRP8MTW6DDW6&pf_rd_t=36701&pf_rd_p=867551807&pf_rd_i=desktop