| major obstacle | 25.81 | A major obstacle is history. | ||
| biggest obstacle | 15.87 | The biggest obstacle is the self. | ||
| main obstacle | 14.02 | Russia is the main obstacle. | ||
| serious obstacle | 6.78 | Serious obstacles remain. | ||
| formidable obstacle | 5.33 | Formidable obstacles. | ||
| legal obstacle | 4.94 | Linh said other legal obstacles also remain. | ||
| remaining obstacle | 4.74 | Yet, Roos is intent on overcoming the remaining obstacles. | ||
| potential obstacle | 4.67 | And a new potential obstacle loomed. | ||
| last obstacle | 4.34 | U.S. removes last obstacle to Iraq oil sale. | ||
| new obstacle | 4.28 | And a new potential obstacle loomed. | ||
| key obstacle | 4.21 | But key obstacles remain. | ||
| huge obstacle | 3.95 | Huge obstacles remain. | ||
| big obstacle | 3.88 | Still, big obstacles remain. | ||
| only obstacle | 3.42 | The only obstacle is money. | ||
| political obstacle | 3.29 | She is no ordinary political obstacle. | ||
| greatest obstacle | 3.03 | For him the greatest obstacle had been bridged. | ||
| bureaucratic obstacle | 2.63 | She made sure there were few bureaucratic obstacles. | ||
| insurmountable obstacle | 2.37 | It seemed an insurmountable obstacle. | ||
| final obstacle | 2.30 | That was the final obstacle. | ||
| significant obstacle | 2.17 | China still has significant obstacles to overcome. |