Sentence:  However , any oxygen nonequivalence would shorten either the already extremely short **f interlayer distance of 2.55 A or the non hydrogen bonded **f interlayer interactions which <WSD>are</WSD> already quite short at 2.58 A . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)