Clear, colourless glass proved extremely difficult to achieve, however.
In bulk materials, however, it has been extremely difficult to achieve covalently bonded junctions between CNTs.
It would require full disclosure of all documents related to the case, which is extremely difficult to achieve.
Calorie restriction — or simply living a life of less in a culture of more — is extremely difficult to achieve and even more difficult to maintain.
For years, cellphone makers had avoided using glass because it required precision in cutting and grinding that was extremely difficult to achieve.
"That target is already extremely difficult to achieve, but it could be done with very hard, very diligent work by every single country," Mr. Oppenheimer said.
The present manual approach for needle insertion and the inherent flexibility of brachytherapy needles makes it extremely difficult to achieve accurate and consistent dosimetry.
An objective of the greatest importance, and extremely difficult to achieve, is the isolation of the pilot's seat in a helicopter.
His views were echoed by Professor Ian Arbon of the Institution of Mechanical Engineers, who said the 2020 target would be "extremely difficult to achieve" and that renewables were nowhere near meeting targets to supply the nation's heating demands.
The proposed overhaul aimed at establishing a new uniform EU asylum and refugee regime, which will be extremely difficult to achieve given national sensitivities and the prominence of immigration issues in national politics across Europe, is unlikely to affect Britain.
But in a 352-page government study released on Tuesday, a committee of the National Research Council warned that successfully using these tools to deter terrorism "will be extremely difficult to achieve" because of legal, technological and logistical problems.
