1. For actio rei vindicatio, a plaintiff must prove: (a) ownership of the property, and (b) that the defendant was in possession when the action was instituted. 2. Where parties stipulate in an agreement's founding provision that the agreement will only become legally binding upon both parties initialing every page and appending full signatures on the last page, failure to comply with this condition precedent renders the agreement invalid and unenforceable. 3. A party relying on an agreement for its rights must both allege and prove the agreement's existence and that its terms (particularly suspensive conditions) were fulfilled. Bare assertions without supporting evidence are insufficient to discharge this onus on a balance of probabilities. 4. Where an agreement contains a suspensive condition requiring confirmation of payment before ownership passes, the party alleging payment must prove both payment and its confirmation. 5. In proceedings involving a juristic person, where there is a dispute on whether the juristic entity transacted with the complainant, it is proper to join the individual who purported to represent the juristic entity as a party, notwithstanding that the individual may have acted as director/agent.