The phrase "remains a difficulty" is grammatically correct and can be used in written English.
It means that something still presents a challenge or obstacle. Example: Despite numerous attempts, resolving this issue remains a difficulty for the team.
Yet for all the growing eco-consciousness there remains a difficulty for the party in its tendency to wallow in hairshirt dreariness.
In addition, effective removal of solvents remains a difficulty when bulk sample instead of films is fabricated.
For example, there remains a difficulty that Ludlow and Segal (2004) have called the residue of the problem of misdescription.
However, how to combine these information items remains a difficulty.
Although it still remains a difficulty for decision, we made the diagnosis of leiomyosarcoma rather than UPS.
Recently, hydrogels have been widely used as carriers for growth factors and cells [ 44, 45], but delivery of the constructs remains a difficulty [ 46].
The question of selecting the adequate parameters of a given appearance model, in order to achieve a desired look, remains a major difficulty for CG artists and designers.
The lack of knowledge about particle behavior in combined sewer detention tanks remains a significant difficulty for the design of these works.
Therefore, it remains a persistent difficulty to accurately predict laminate failure under combined loading by using either unidirectional composite (ply) data or with basic constituent material properties.
Among these problems, the perfect-reconstruction (PR) theory of the 2D DFT modulated filter bank with arbitrary modulation and decimation matrices remains an unsolved difficulty, which is the focus of this paper.
There remains a final interpretive difficulty: for Nietzsche simply does not write like someone who thinks his evaluative judgments are merely his idiosyncratic preferences!
