It has taken until now to pin down its exact location.

一直到现在才确定了它的准确位置。

The cause of the disease is difficult to pin down precisely.

病因目前还难以解释清楚。

Mr Obama's views are hard to pin down.

奥巴马先生的观点则很难确定。

But it is always hard to pin down.

但这始终是难以确切说明。

Other causes are harder to pin down.

其它原因就很难下定论了。