It was the principal obstacle encountered by the missionaries in the rural places.

The principal remaining obstacle in this enterprise is the unknown relation between genes and culture.

And diplomats say those parties are often the principal obstacles to peace.

He has also long been the principal obstacle to legislation that would strengthen protection for designs.

Critical theory maintains that ideology is the principal obstacle to human liberation.

The principal obstacle has always been in the Senate, supporters of the bill agree.

Experts argue, though, that race is not the principal obstacle to integration.

Popular access to higher education slowly began after 1914, yet the principal remaining obstacle was its expense.

Soviet emigre scientists say the principal obstacles are lack of contacts and American job experience.

Another of the principal obstacles to finalising the arrangements for the marriage was financial.