Cooper, Roger A. <br/><br/>
The Ordovician time scale - calibration of graptolite and conodont zones 

 - Prague  Univerzita Karlova  1999 
 - pp. 1-4  ilus. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>BIOESTRATIGRAFIA<br/>CONODONTA<br/>GRAPTOLITES<br/>ORDOVICICO