GuidanceEC 1105-2-407: Planning Models Improvement Program: Model Certification(CECW-CP, 31 May 2005) Interim Guidance for PCX’s to Proceed with Model Certification (7 September 2006) ECB 2007-6: Model Certification Issues for Engineering Software in Planning Studies (CECW-CE, 10 April 2007) Memorandum: Policy Guidance on Certification of Ecosystem Output Models (August 13, 2008) - This memorandum establishes additional policy and procedures regarding the certification requirements for ecosystem output models used in all planning activities, and serves as a supplement to EC 1105-2-407