Jansy Mello sends this tidbit:

 

Dear List,

I just found out know that Nabokov wrote an "Introduction" to
R.L.Stevenson's Dr. Jekyll and Mr. Hyde*.
A few months ago I discovered that an entire collection of Chekov's
magnificent stories (translated and published in Portugal) announces a
preface by V.Nabokov. However, from its reproduction in the first volume
(among more than twelve others in which VN's "preface" is mentioned on the
back covers), I saw that the  so-called preface is merely an excerpt from
Nabokov's Russian Lectures.
I'm in doubt if this "introduction" falls under the same category and was
not originally intended to appear as an "introduction".
If the text is not the same as the one found in VN's Lectures on English
Literature,  how is it possible to get a copy of it?

*Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson, Dan Chaon (Afterword) ,
Vladimir Nabokov (Introduction) , Vladimir Nabokov
Paperback - Reissue
ISBN-13: 9780451528957
Pub. Date: September 2003
Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson, Vladimir Vladimirovich
Nabokov, Vladimir Nabokov (Introduction)
Mass Market Paperback - Reprint
ISBN-13: 9780451523938
Pub. Date: August 1994