It had proved difficult to make the poster eight times bigger than the picture in the book and still maintain the right proportions.
It may also prove difficult to make large profits from other large recent gas discoveries, for example in African countries like Mozambique and Tanzania.
Unfortunately for Baldini, it is proving difficult to make that argument stick, such is the suspicion towards anything coming out of Rome.
Kapoor, who immediately recognised its artistic potential, has been working with the pigment since 2014 but says it's proving difficult to make sufficient quantities to apply to any artworks, because of its density.
Tonight, a senior Clinton administration official said that in the first two-and-a-half-hour session, Mr. Arafat covered such a range of questions that it proved difficult to make progress.
Riemann's ideas were both profound and naïve, and for that reason they proved difficult to make precise, but we can content ourselves with being naïve initially.
But although the techies have come up with a way to revolutionise urban mobility, and though the list of compelling reasons why it makes sense can only grow longer, it could still prove difficult to make it happen - even with the urban planners on-board.
The episode proved difficult to make.
The climax of the film also proved difficult to make.
The Weismann unit proved difficult to make reliable and was used alongside the original gearbox, mainly on a spare chassis, until the Dutch Grand Prix, after which it was put to one side.
