Assertion: specific impurity | /r/HasProperty | a-a
Facets:
Source sentences:
text: The specific impurities (V), (IV), (XIII a) and (XIII b), or their free acids (V-A), (IV-A) (XIII a-A) and (XIII b-A) are characterized by their mutual structural similarity as well as structural similarity to montelukast, which makes their isolation more difficult.