The phrase "a key difficulty in" is correct and usable in written English.
It can be used when discussing a significant challenge or obstacle related to a specific topic or situation.
Example: "A key difficulty in implementing the new software system is ensuring that all employees are adequately trained."
Alternatives: "a major challenge in" or "a significant obstacle in".
Characterizing the set of such equilibria is a key difficulty in studying this problem.
For the latter, lack of relative motion is identified as a key difficulty in the association process.
A key difficulty in optimization under uncertainty is in dealing with an uncertainty space that is huge and frequently leads to very large-scale optimization models.
A key difficulty in the spatial discretization process is maintaining a balance between the aggregation-induced information loss and the increase in computational burden caused by the inclusion of additional computational units.
These results underscore a key difficulty in simulation studies: unless simulations accurately model the genetic architecture and population history of QTL alleles, they will have limited relevance to empirical datasets.
A key difficulty in any assessment of life quality is that it is bound up with individual expectations.
A key difficulty resides in studying these mechanisms in vivo, and in untangling factors intrinsic to CF (compared to other diseases with similar neutrophilic inflammation, such as COPD), and those affected by exogenous drugs.
"A key difficulty for home buyers in New Jersey," she said, "has been that a lot of the service people they call don't show up -- or the attitude is 'I'll be out when I can.' "We continually check to make sure the people on our list are reliable and responsive," she added.
A key difficulty is that Mei Xiang places herself in what he called "pancake position" — flat on her stomach, legs outstretched — and Tian Tian isn't assertive enough to lift her off the ground.
A key difficulty for mosquito SIT is sterilization.
The key difficulty in conducting an IV analysis is finding and justifying a strong instrument, especially if the research questions revolve around multiple instruments and predictors.
