Editing Property Selectors (section)

===General===
The items in a list of identifiers are separated by plus signs (+) only. Do not add spaces within a list of identifiers. The selector '''resi''' takes (+)-separated lists of identifiers, as in
<source lang="python">
PyMOL> select nterm, resi 1+2+3
</source>
or, alternatively, it may take a range given with a dash
<source lang="python">
PyMOL> select nterm, resi 1-3
</source>
The identifier for a blank field in an input file is an empty pair of quotes
<source lang="python">
PyMOL> select unstruct, ss ""   # A named selection is created
                                # to contain all atoms that are not assigned 
                                # a secondary structure.
</source>