Description: Contains a reference to IDs of possible preceding questions. The "qstn" IDREFS may be used to specify the question IDs.
Example(s):
<var><qstn><backward qstn="Q12 Q13 Q14 Q15">For responses on a similar topic, see questions
12-15.</backward></qstn> </var>
<var><qstn><backward qstn="Q143"> </backward></qstn> </var>