Sentence examples for has been difficult to prove from inspiring English sources

Russia's military intervention in Ukraine has been difficult to prove beyond a doubt.

But this notion has been difficult to prove because the main symptoms of the disorders, severe social withdrawal in autism and low I.Q. in mental retardation, are generally not diagnosed until children are around 3 years old.

But with scant data from the waters around Antarctica, that has been difficult to prove.

Many theorists have predicted that sympatric speciation is also possible, but the phenomenon has been difficult to prove.

Environmental cleaning is a fundamental principle of infection prevention in hospitals, but its role in reducing transmission of health care-acquired pathogens has been difficult to prove experimentally.

But it has been difficult to prove a link between the virus and the birth defects because blood tests for Zika virus are only accurate for about a week after infection.

And since the crop was on county land, it would have been difficult to prove who was tending them unless someone was actually harvesting them.

Ms. O'Connell told him that it would have been difficult to prove that Mr. Afzal had a seizure just before the car crashed, Mr. Ricco said.

Mr. Jaccarino was so drunk, Ms. Walton told Judge Melissa A. Crane, that it would have been difficult to prove that he meant to assault Ms. Soler.

Mr Mazuz also said some of the allegations would have been difficult to prove in court and might have damaged the "image of the state of Israel".

The evidence showed that the companies clearly "intended" their cigarettes to deliver nicotine in doses that would "affect" the body, a proposition that had been difficult to prove before.