"is yet difficult" is a grammatically correct and usable phrase in written English.
It can be used to describe something that is currently difficult, but may become easier in the future. It can also convey a sense of ongoing difficulty, despite efforts to make it easier. Example: "Although I have been practicing for weeks, the piano piece is yet difficult for me to play perfectly."
As one of the major anthropogenic influences, vegetation change unavoidably alters surface property and subsequent the terrestrial water cycle, while its contribution is yet difficult to isolate from the mixed influences.
In that context, it is yet difficult to understand how the Kasalath allele of NADH-GOGAT1 conferring less activity than the japonica one could dominantly affect susceptibility (Figure 4B).
These studies raise interesting questions about the temporal aspects of preferences, but it is yet difficult to conclude about the added value of such measurements, mainly because of a lack of systematic approaches with similar food stimuli.
It is, yet, difficult to explain how BTD is down-regulated in breast cancer plasma.
Our findings show that while a number of randomized trials have investigated psychological treatments for depression in primary care patients it is yet difficult to decide whether some treatments should be considered more effective than others.
However, ECM gene data are yet difficult to interpret since little is known about the function of most of the proteins encoded by these genes in matrix mineralization.
Forecasting ionospheric characteristics during disturbed periods that accompany space weather events is yet more difficult.
The result is yet another difficult day for the stock (NASDAQ FB).
However, for general large-scale nonlinear networks it is yet very difficult, and often impossible, both computationally and analytically, to find Lyapunov functions.
The detection of the FECG is yet a difficult task even when the maternal component of the signal has been reduced.
For all that, the difficult part is yet to come.
