Sentence:  Clearly, there is no solution to the problem of spurious center-of-mass motion in the nonseparable case. Mathematically it is not even a well-defined problem. The only course is to be very careful not to draw conclusions which may be dependent on the <WSD>spuriosity</WSD> of the states in question. In particular, the <WSD>spuriosity</WSD> should be checked by evaluating &lt;H<sub>em</sub>&gt; for the final eigenstates. 
Meaning of the word marked with <WSD> tags:  Spuriousness.