The comma after "srva" must be removed for the bib to be accepted.

    OK: author = "sanu, LBL, srva SKEW/CPS",
Not-OK: author = "sanu, LBL, srva, SKEW/CPS",

Why?

@misc{sanu,
author = "sanu, LBL, srva, SKEW/CPS",
title = "Invasive, gebietsfremde Pflanzen (Neophyten) in der Schweiz: Bedürfnisse der Anspruchsgruppen aus der Praxis",
howpublished = "(\url{http://www.cps-skew.ch/deutsch/inva_ws_05.pdf})",
year = 2005,
}