private BitSet selectElements(String str) {

		if ("selected".equalsIgnoreCase(str))
			return model.getAtomSelectionSet();

		BitSet bs = genericSelect(str);
		if (bs != null)
			return bs;

		int noa = model.getAtomCount();
		bs = new BitSet(noa);

		String[] s = str.split(",");
		for (int i = 0; i < s.length; i++)
			s[i] = s[i].trim();

		for (int i = 0; i < noa; i++) {
			Atom a = model.getAtom(i);
			for (String x : s) {
				if (a.getSymbol().equalsIgnoreCase(x)) {
					bs.set(i);
					break;
				}
			}
		}

		model.setAtomSelectionSet(bs);

		return bs;

	}