1.   An unknown factor, analysts said, is the tribulations of the ruling Conservative government.

2.   Its position will also depend on the whereabouts of the bridge across the river, which is another unknown factor.

3.   Research has indicated that narcoleptics have a set of genes that are triggered by unknown factors to cause narcolepsy.

4.   The unknown factor is the cost of copper.

5.   The unknown factor is whether this absence will force the national selectors to look elsewhere.

6.   The present study indicates that H pylori infection is not the unknown factor.

7.   An unknown factor is what the Mexican government will do if large numbers of Central Americans cross into Mexico on their way to the United States.

8.   An unknown factor is who in the Chinese leadership is making the decisions.