https://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2015-2016/0968.html
namd-l: Re: Atomselect within radial pair distribution function g(r)
namdlwithin
https://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2004-2005/2687.html
namd-l: Re: How to atomselect several residues
how tonamdlresidues