public List<Employee> getCoWorkers(int id, String name){
		if (name == null) throw new IllegalArgumentException();
		TreeNode e = find(id, name);
		if (e == null) return null;
		List<Employee> coWorkers = new ArrayList<Employee>();
		if (e.getSupervisor() != null) {
			for (TreeNode n: e.getSupervisor().getWorkers()) {
				if (n.getEmployee() != e.getEmployee()) {
					coWorkers.add(n.getEmployee());
				}
			}
		}
		return coWorkers;
	}