[phenixbb] the input for atom selection

Dear All, By the Graphics of phenix refine, I want to select all the atoms of the first 2 residues, will you please what I should to input in the "Selection" item? If I want to select all the atoms of both the first 2 residues and the last 2 residues, what should I input? Suppose I have a chain with 20 amino acids, and as expected the density of the first 2 residues and the last 2 residues are low, by occupancy refinement can I make the conformation of the first 2 residues and the last 2 residues reliable? Cheers, Dialing