There is no way to comment out BibTeX values, just use a non-standard name.

diff --git a/src/apparatus/main.bib b/src/apparatus/main.bib
index 1d2f8db4798b5a740ae68edf3b5f4e006d0ed173..ff731407e6dfe847d0c7dfc19eaf7df7665c8cb3 100644 (file)
--- a/src/apparatus/main.bib
+++ b/src/apparatus/main.bib
@@ -18,6 +18,6 @@
   title = "SURE 2 Supercompetent Cells",
   year = 2012,
   url = "http://www.chem.agilent.com/en-US/Search/Library/_layouts/Agilent/PublicationSummary.aspx?whid=72739&liid=6524",
-  % http://www.genomics.agilent.com/CollectionSubpage.aspx?PageType=Product&SubPageType=ProductDetail&PageID=663
+  alternative_url = "http://www.genomics.agilent.com/CollectionSubpage.aspx?PageType=Product&SubPageType=ProductDetail&PageID=663",
   note = "Catalog #200152.",
 }