89 12. Goodwill and other intangible assets  A summary of activity for intangible assets for the years ended 31 December 2012 and 2011 is as follows:  Goodwill Other intangible assets  US$000 Customer related  intangible assets US$000 Purchased software,  licenses and other US$000 Patents  US$000  Intangible assets from  internal development US$000 Total US$000 Cost  Balance at 31 December 2010 / 1 January  2011  – – 21,149 1,309  5,951 28,409 Additions relating to the SiTel acquisition  32,283 14,100 525 3,696  14,654 32,975 Effect of movements in foreign currency  – – (58) –  (30) (88) Additions  – – 5,175 759  5,165 11,099 Reclassifications  – – – –  – – Disposals  – – (554) (10) (210) (774) Balance at 31 December 2011 / 1 January  2012  32,283 14,100 26,237 5,754  25,530 71,621 Effect of movements in foreign currency  – – 96 –  – 96 Additions  – – 26,606 950  5,956 33,512 Reclassifications  – – – –  – – Disposals  – – (725) – (387) (1,112) Balance at 31 December 2012  32,283 14,100 52,214 6,704  31,099 104,117 Amortisation and impairment losses  Balance at 31 December 2010 / 1 January  2011  – – (14,783) (183) (2,716) (17,682) Effect of movements in foreign currency  – – 48 – 30 78 Amortisation charge for the year  – (5,428) (2,650) (939) (7,013) (16,030) Impairment charges  – – – –  – – Disposals  – – 158 6  210 374 Balance at 31 December 2011 / 1 January  2012  – (5,428) (17,227) (1,116) (9,489) (33,260) Effect of movements in foreign currency  – – (50) –  – (50) Amortisation charge for the year  – – (10,273) (1,135) (8,185) (19,593) Impairment charges  – – – –  – – Disposals  – – 575 –  – 575 Balance at 31 December 2012  – (5,428) (26,975) (2,251) (17,674) (52,328) Net book value  At 31 December 2010 / 1 January 2011  – – 6,366 1,126  3,235 10,727 At 31 December 2011 / 1 January 2012  32,283 8,672 9,010 4,638  16,041 38,361 At 31 December 2012  32,283 8,672 25,239 4,453  13,425 51,789