Gray, J. <br/><br/>
Land plant spores and the Ordovician-Silurian boundary 

 - London  British Museum (Natural History)  April 1988 
 - pp. 351-358 
<br/><br/><label>ISSN: </label>0007-1471 
<br/><br/><label>Subjects--Topical Terms: </label><br/>ORDOVICICO<br/>PALINOLOGIA<br/>POLEN Y ESPORAS<br/>SILURICO