queries for comparing substructure search engines

Dear all,
 Has anyone ever compiled a list of substructure search queries that one can
 use to compare different database search engines? Also, some bibliography
 on the subject (peer-reviewed publications rather than commercial blurbs)
 would be greatly appreciated as well. SMARTS would be ideal.
 Thanks in advance.
 Dimitris K. Agrafiotis, PhD              | E-mail: agrafiotis %-% at %-% 3dp.com
 3-Dimensional Pharmaceuticals, Inc.      | Tel:    (610) 458-6045
 665 Stockton Drive, Suite 104            | Fax:    (610) 458-8249
 Exton, PA 19341                          |