?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.au=+Nestra+H%C3%A4rmel&rft.aulast=Nestra&rft.aufirst=H%C3%A4rmel&rft.date=2002&rft.volume=15&rft.issue=4&rft.title=Acta+cybernetica&rft.atitle=A+framework+for+studying+substitution&rft.issn=0324-721X&rft.pages=633-652&rft.genre=article