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:
| Source | Date | Cardwell | Jones | Knight | Lanier | Martin |
| --- | --- | --- | --- | --- | --- | --- |
| Insider Advantage | July 8–9, 2008 | 11% | 20% | 4% | 1% | 31% |
| Strategic Vision (R) | June 27–29, 2008 | 22% | 25% | 14% | 6% | 17% |
| Mellman Group (D) | May 29, 2008 | 7% | 16% | 2% | 3% | 21% |
| Insider Advantage | May 12, 2008 | 14% | 21% | 1% | 5% | 3% |
| Strategic Vision (R) | May 9–11, 2008 | 20% | 28% | 11% | 5% | 15% |
Question:
What source has a cardwell of 20%?
Answer:
Strategic Vision (R)