knotty question

Edmund did not look puzzled; he was deciding no knotty question at this moment.

As to what attracts them in their favourite literature, that is a much more knotty question.

Until this knotty question is satisfactorily solved, they forbear pronouncing the last munter or prayer.

Here the knotty question arose again, what territory they, the Arabs, would give to Manua Sera?

After this knotty question was settled an incident almost incredible in its awful gruesomeness took place.