@techreport{Sae04,
author = {F. S\'aenz-P\'erez},
institution = {Facultad de {I}nform\'atica, {U}niversidad {C}omplutense de {M}adrid},
note = {{\tt http://www.fdi.ucm.es/profesor/fernan/DES/}},
number = {Technical Report 139-04},
title = {Datalog {E}ducational {S}ystem {V1.1.} {U}ser's {M}anual},
year = {2004}
}