Predhovor
Dokonalé a spriatelené čísla, GDML_Books, (1969), p. 3-4 / Harvested from
Access to full text
Full (PDF) 
@inbook{403667,
     title = {Predhovor},
     booktitle = {Dokonal\'e a spriatelen\'e \v c\'\i sla},
     series = {GDML\_Books},
     publisher = {Mlad\'a fronta},
     address = {Praha},
     year = {1969},
     pages = {3-4},
     language = {sk},
     url = {http://dml.mathdoc.fr/item/403667}
}

 (éd.). Predhovor, dans Dokonalé a spriatelené čísla, GDML_Books,  (1969), pp. 3-4. http://gdmltest.u-ga.fr/item/403667/