Butels, J. <br/><br/>
Geomagnetic indices K and C, 1955 
J. Bartels, A.Romana and J.  Veldkamp                                               
 - Holland  1961 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Geomagnetic Indices
<br/><br/><label>Universal Decimal Class. No.: </label>083.550.38  / IAGA-12I