When using third-party software developers, the most effective method of providing software development Quality Assurance (QA) is to perform overlapping code reviews by both parties. Code reviews are the process of examining the source code of an application for quality, functionality, security, and compliance. Overlapping code reviews by both parties means that the code is reviewed by both the third-party developers and the contracting organization, and that the reviews cover the same or similar aspects of the code. This can ensure that the code meets the requirements and specifications, that the code is free of defects or vulnerabilities, and that the code is consistent and compatible with the existing system or environment. Retaining intellectual property rights through contractual wording, verifying that the contractors attend development planning meetings, and creating a separate contractor development environment are all possible methods of providing software development QA, but they are not the most effective method of doing so. References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 8, Software Development Security, page 1026. Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 8, Software Development Security, page 1050.