You can add a new person with the name "\Third World Congress of Structural and Multidisciplinary Optimization Proc. Third World Congress of Structural and Multidisciplinary Optimization\,", or you can "\Third World Congress of Structural and Multidisciplinary Optimization Proc. Third World Congress of Structural and Multidisciplinary Optimization\," with a person entry that is so far only been referred to by another name (such as a former name or an alias name).