Application of inductively coupled plasma atomic emission spectroscopy analysis with a polychromator/monochromator combination to the by-products of coal-fired power stations / C.A. WeersMulti trace element analysis of dry biological materials by neutron activation analysis including a chemical group separation / [by] Carolus Adrianus WeersMulti trace element analysis of dry biological materials by neutron activation analysis including a chemical group seperation / by C.A. Weers