?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.au=+Alvarez+Ramis+Concepci%C3%B3n&rft.aufirst=Concepci%C3%B3n&rft.aulast=Alvarez+Ramis&rft.title=Plant+cell+biology+and+development&rft.issn=0866-5443&rft.date=1995&rft.volume=6&rft.atitle=Characterization+of+different+forms+of+organic+matter+in+Upper+Cretaceous+levels+from+Cerro+de+La+Mesa+(Madrid%2C+Spain)&rft.pages=33-43&rft.genre=article