Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Date | Tournament | Winning score | Margin of victory | Runner(s)-up |
| --- | --- | --- | --- | --- |
| 12 Dec 2004 | Dunhill Championship 1 | –7 (71-69-70-71=281) | Playoff | Neil Cheetham |
| 29 Apr 2007 | Open de España | –16 (69-68-68-67=272) | 1 stroke | Jyoti Randhawa |
| 12 Oct 2008 | Madrid Masters | –19 (69-64-66-66=265) | 3 strokes | Ricardo González |
| 10 Jan 2010 | Africa Open 1 | –20 (67-70-68-67=272) | 1 stroke | Thomas Aiken |
| 17 Jan 2010 | Joburg Open 1 | –23 (63-68-64-66=261) | 6 strokes | Darren Clarke , Keith Horne |
| 16 Jan 2011 | Joburg Open 1 | –19 (68-61-69-67=265) | 1 stroke | Garth Mulroy |
| 10 Apr 2011 | Masters Tournament | –14 (69-71-68-66=274) | 2 strokes | Jason Day , Adam Scott |
| 16 Dec 2012 | Alfred Dunhill Championship 1 | –24 (67-64-64-69=264) | 12 strokes | Kristoffer Broberg |
Question:
Which tournament had a margin of victory of 6 strokes?
Answer:
Joburg Open 1