(in millions of US dollars except share and per-share amounts)
10. Intangible Assets and Goodwill
| 2007 | 2006 | |||
| Intangible assets – net of accumulated amortization of $27.9 (2006 – $22.6) | $ | 24.5 | $ | 29.3 |
| Goodwill – net of accumulated amortization of $7.3 (2006 – $7.3) | $ | 97.0 | $ | 97.0 |
Intangible assets relate primarily to production and technology rights and computer software. Other than goodwill, the company has not recognized any intangible assets with indefinite useful lives. Total amortization expense relating to finite-lived intangible assets for 2007 was $6.1 (2006 – $6.9; 2005 – $4.1). Amortization expense in each of the next five years calculated upon such assets held as at December 31, 2007 is estimated to be $3.9 for 2008, $3.8 for 2009, $3.3 for 2010, $1.0 for 2011 and $1.0 for 2012.
Substantially all of the company's recorded goodwill relates to the nitrogen segment.