Sometimes we need to do more complex searches, so we use the advanced search form. For example, we'll search for all sites containing *Zn or Cu* with a metal coordination number of *4 or 5*, the set of ligands to the metals should contain *at least 2 His and 1 Asp*, and the structures should have been *from 1997 to 2002* and have a resolution in the *0.9 - 2.5 Angstroms* range. We now find a more manageable set of sites, roughle ten times smaller than what we got using the simple search form.