The chief difficulty lay in making the first contact between the machines.

But to buy the machine, it was necessary to find the inventor; and there seemed the chief difficulty.

Our chief difficulty will be in finding some one on whom the Brain can place the blame.

The chief difficulty came because of Japan's demand for a money indemnity.

Montgomery's chief difficulty was to find time for his training without any interference from the doctor.

From Norman's point of view, the chief difficulty would come after the seaplane had landed.

A chief difficulty, every day Glen logged in space, was trying to find ways to look busy.

The chief difficulty, as usual with the English in those days, was lack of money.

His chief difficulty, of course, was to find anyone to play with him.

The chief difficulty I foresaw was that the machine must remain.