Vizmuller, Peter.  <br/><br/>
Filters with Helical and Folded Helical Resonators /  
Vizmuller Peter. 
 - Norwood, MA :   Artech House,   1987. 
 - VIII, 107 s.:   il.;   24 cm. 
<br/><br/><label>ISBN: </label>0890062447