RFC 1131 "The OSPF Specification" is available only in PostScript form in the file RFC 1131.PS To obtain this file via the NIC's automatic mail server SERVICE, use the Subject line: SEND RFC:RFCnnnn.PS (where nnnn is the number of the RFC you wish to obtain).
RFC 1131 - unabridged
Unabridged RFC 1131:
Czech version: RFC 1131