| Share | Phrase |
|---|
| 32.31% | underlying [location] problem |
| 22.83% | underlying [location] concept |
| 12.36% | underlying [location] surface |
| 12.02% | underlying [location] principle |
| 6.76% | underlying [location] flame |
| 6.05% | underlying [location] layer |
| 5.99% | underlying [location] material |
| 1.64% | underlying [location] member |