It is difficult to preserve something that was made to vanish".
But the French Revolution proved that it is difficult to preserve epic economic imbalance.
But "peace" was difficult to preserve on both the domestic and foreign fronts.
The President is reported to have said that unless Congress enacted a new measure it would be difficult to preserve peace with Mexico.
Because vitamin C is easily destroyed by reactions with oxygen, especially in neutral or alkaline solution or at elevated temperatures, it is difficult to preserve in foods.
"When the real estate market is high it's difficult to preserve this resource," said James A. Krauskopf, president of the Corporation for Supportive Housing, a national organization that supports service-enriched housing for homeless and disabled people.
"I worry every day about the homogenizing forces at work in my professional life," she said, adding that it can be difficult to preserve creativity within cable's production process.
The problem was that some species couldn't survive outside their natural habitat, and were difficult to preserve, not least because 19th-century techniques for, say, pickling sea creatures, were so sketchy.
These structures are difficult to preserve.
However, due to inadequate understanding of brand by engineering, design and marketing, brand statement is difficult to preserve.
The structural organization of oral soft tissue and its relationship with highly calcified teeth are difficult to preserve unless tissues are decalcified, paraffin embedded and subsequently sectioned.
