The IF/Prolog V5.3 Manuals:

Installation Guide
pdf [138 kB]
Users Guide
pdf [1.398 kB]
Reference Manual
pdf [2.483 kB]
Constraint Technology
pdf [546 kB]
Windows specific Interfaces
pdf [533 kB]
Java Interface
pdf [513 kB]
SQL Interface
pdf [226 kB]
OSF/Motif Interface
pdf [1.524 kB]