Seems like it sometimes returns incorrect publish date (other thant in LubimyCzytac.pl, or in
http://www.worldcat.org), and even if Published date is unchecked in preferences.
For example it returns 1995 (should be 1997) for:
http://lubimyczytac.pl/ksiazka/48615/
P.S.
Anyway this plugin is otherwise very useful for me.
Update:
Some technical data:
calibre 0.8.33
Vista Ultimate x64