Correct footnote:

Your footnote above should look like this:

D. W. Robertson, Jr, *A Preface to Chaucer: Studies in Medieval Perspectives* (Princeton: Princeton University Press, 1962), pp. 101-14.

In your own work, the same footnote would look like this:

D. W. Robertson, Jr, A Preface to Chaucer: Studies in Medieval Perspectives (Princeton: Princeton University Press, 1962), pp. 101-14.

Comment:

For this text you could have given the place of publication either as 'Princeton, NJ' or simply 'Princeton'. As there is little room for confusion here, we suggest you simply use 'Princeton'.

Note there is no full stop after 'Jr': this is because 'Jr' is a contraction (of Junior), not an abbreviation.

Remember that there should be a space between initials: so D. W. not D.W..