difficult to classify

References in classic literature ?
Rebecca in particular was so difficult to classify that Miss Dearborn at the end of a fortnight gave up the attempt altogether.
In the same way that the label "Asian cuisine" hides diversity of tastes and methods, it's equally difficult to classify "Native American cuisine" as a single genre.
Because being gay is considered by some to be a sin, it theoretically puts a person's soul at risk (again, as a sin it is considered a conscious choice made by the individual -- it would be difficult to classify sexual orientation as a sin if it wasn't believed to be a choice).
Intra-chromosomal variations, like CNVs, are more difficult to classify as disease causing, because similar diseases may be caused by a variety of different mutations.
While the Middle East region is difficult to classify into one category in terms of demand for consulting services, Shehadi said that all countries across the region shared the need to create more jobs and expand underdeveloped health care and education infrastructures.
So it's very difficult to classify something that you can't fully characterize.
It is quit difficult to classify “Through The Waters” in one particular Genre.
While describing the cuisine at his eponymous restaurant, Anand said that it's very difficult to classify the cuisine, but it can be called "progressive cuisine" as basically it's about putting old school and new school together.
But these central and recurring concerns are not only related but imbricated in Corkery's writings, making it difficult to classify a particular essay under a particular heading.
Timeless and restrained without shying away from being dance-floor forward, cuts from artists like Kingdom, L-Vis 1990, Girl Unit, and Rizzla are difficult to classify, a blessing at a time when genres rise and fall in a matter of months.
Regarding environmental issues, I find it difficult to classify the basic gas that sustains life on the planet ([CO.
Amos said it is difficult to classify the human disasters and compare regions, because in each case an individual faces some kind of emergency or disaster situation and needs help, she said.