code: public List<Matrix4d> getElementaryAxes(){
  		List<Matrix4d> ops = new ArrayList<Matrix4d>(getNumLevels());
  		for(Axis axis : axes) {
  			ops.add(axis.getOperator());
  		}
  		return ops;
  	}
docs: Return the operator for all elementary axes of symmetry of the structure, that is,
  the axes stored in the List as unique and from which all the symmetry
  axes are constructed.
  
  @return axes elementary axes of symmetry.