The phrase "and difficult to establish" is correct and usable in written English.
It can be used when discussing something that is challenging to set up, create, or prove.
Example: "The criteria for success in this project are vague and difficult to establish."
Alternatives: "and hard to define" or "and challenging to determine".
A major obstacle to entering the food industry is the legal requirement to work in a licensed commercial kitchen, which is expensive and difficult to establish on one's own.
In conclusion, the diagnosis of ISI is long and difficult to establish.
In cases where measurement of QOL is a secondary endpoint, sample size calculations are rare and difficult to establish.
Relationships between blood and brain lactate concentration, lactate oxidation and extent of inhibition of glycolysis are complex and difficult to establish in vivo.
Block success evaluations in regional anesthesia studies are time consuming (repetitive sensible testing of heat and cold, pin prick testing, and motor function measurements every 5 min for at least 60 min) and difficult to establish in prospective cohort evaluations.
Sent interlocks offer particularly knowledge-based and social influence benefits that firms cannot realize via received and undirected interlocks, but are in general costlier and more difficult to establish.
Exactly how many landlords would be affected is unclear, and remains difficult to establish while privacy rights in Germany restrict centralised access to the land registry.
"With the situation in the Jenin refugee camp changing by the day, it will become more and more difficult to establish with any confidence or accuracy the 'recent events' that took place there".
Either way, it's difficult to discern when exactly the pictures were posted online, and therefore difficult to establish a true "dick game".
The binding motifs for many transcription factors are not yet known and are difficult to establish by direct in vivo or in vitro experiments.
Of course, the dose that can create such a "slightly hostile but still acceptable" environment varies among patients and is difficult to establish, although it is required.
