code: public Pair<List<Group>> getSurfaceResidues(double minAsaForSurface) {
  		List<Group> surf1 = new ArrayList<Group>();
  		List<Group> surf2 = new ArrayList<Group>();
  
  		for (GroupAsa groupAsa:groupAsas1.values()) {
  
  			if (groupAsa.getAsaU()>minAsaForSurface) {
  				surf1.add(groupAsa.getGroup());
  			}
  		}
  		for (GroupAsa groupAsa:groupAsas2.values()) {
  
  			if (groupAsa.getAsaU()>minAsaForSurface) {
  				surf2.add(groupAsa.getGroup());
  			}
  		}
  
  		return new Pair<List<Group>>(surf1, surf2);
  	}
docs: Returns the residues belonging to the surface
  @param minAsaForSurface the minimum ASA to consider a residue on the surface
  @return