[1]
Chris Ryan, Under Cover (Agent 21). Red Fox, 26AD [Online]. Available: 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. Red Fox, 10AD [Online]. Available: 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