Sentence examples for proven difficult to from inspiring English sources

But her popularity has proven difficult to transfer.

But safety advocates say it has proven difficult to improve the situation.

SUMMARY: A group of special interest to mammalogists, taxonomists, and systemicists, ungulates have proven difficult to classify.

But what the military has regarded as a turning point in the Iraq war has proven difficult to emulate.

Those cuts have proven difficult to implement, as have promises to eliminate Amtrak subsidies and cuts to food stamps.

Performance pay has had mixed results, and it has proven difficult to systematically separate good and bad teachers.

Most sighted animals perceive motion automatically, but the exact brain mechanism underlying this ability has proven difficult to pin down.

However, spectroscopic evidence has proven difficult to obtain.

However, efficient admissible heuristics have proven difficult to find.

Consequently, it has proven difficult to maintain surfactant-producing cells [9].

Unfortunately, it has proven difficult to clarify the relevance of this difference.