Part I of the problem, on the other hand, had proved quite intractable.

Administration officials have a variety of theories as to why this dispute is proving so intractable.

The dispute that has proved intractable so far is the definition of the federation.

The expanding research efforts are trying to answer some questions, but many of the difficulties may prove intractable.

Tony's learning difficulties and in particular his own attitude to them, proved more intractable.

And like all such problems, this one, too, has proved intractable.

Because the issues proved so intractable this time, the leaders ended up doing more of their own negotiating than usual.

But the issue of the developing countries' future role has proved intractable so far.

But the issue has proved especially intractable in New Hampshire.

Its problems proved intractable and the program was canceled in the summer of 1946.