The phrase "are often difficult to identify" is correct and usable in written English.
It can be used when discussing subjects, issues, or phenomena that are not easily recognized or understood.
Example: "Certain emotions are often difficult to identify, especially when they are mixed with others."
Alternatives: "are frequently hard to pinpoint" or "are commonly challenging to recognize".
Breaches of principles are often difficult to identify – not because someone is 'evil' and purposely misleading the auditors, but because the human element can be hard to quantify and rate.
The coastal areas of the west, north, and south might be expected to show African cultural elements, but, apart from some Bantu words, these are often difficult to identify conclusively.
Numerous interactions occur between soil, crop, and climate, which are often difficult to identify and manage.
However, in actually observed ground magnetometer data, FLR-generated ULF waves are often difficult to identify due to superposed non-FLR signals (mainly compressional-type).
However, the respective roles of these various control factors in modifying sediment storage and channel stability are often difficult to identify.
There are a number of possible causes for this increase; moreover, as the symptoms of depression in the elderly are often difficult to identify and interpret, a diagnosis of depression in the elderly may be difficult to make, particularly when other concomitant pathologies mask the signs and symptoms of this disease.
Part of the problem is that it is often difficult to identify a suicide bomber.
In cases of extreme partisanship in gerrymandering, it is often difficult to identify the original sin.
Because Viola freely hybridize, however, it is often difficult to identify their species.
It is often difficult to identify exactly who or what leads to the rise or fall of regulatory reforms.
For this reason, it is often difficult to identify the family into which a genus should be placed without laboratory analysis.
