Beekeepers interested in the use/not use of oxalic acid might
have a
look at the work of Danish scientists on the site below belonging
to a
branch of the Danish Department of Agriculture.
The site is in danish, but the article is in english :-)
You have to subscribe to look at all the pages, but the article
is
freely available by following this procedure:

1 - go to www.planteinfo.dk
2 - click the grey button with PL@NTEINFO DIREKTE written on it
3 - click the link SYSTEMER in the left frame
4 - click the link BIAVL in the left frame (biavl is beekeeping)
5 - click the link OXALSYRE in the right frame

This will lead You to an article - about the subject. I think You
will
find it interesting.

Kind regards,
Lars Hansen
Denmark