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ISO 9011 is often confused with ISO 9001 just because of the numbering used for the standard. In fact, the ISO 9011 standard has nothing to do with management systems (which the ISO 9001 document defines), but instead is one of many sets of requirements published by the International Organization for Standardization (ISO) that defines the necessary quality requirements for producing a product. In the case of ISO 9011, the product is synchronous belt drives for automotive pulleys. If you need to know what the automotive industry requires for these belt drives, then this is the standard you should get.
ISO 9001 includes requirements for developing and implementing a quality management system based on improving customer satisfaction. For information on the ISO 9001 quality management system standard, see What is ISO 9001.
ISO 19011 is also a standard published by the international organization for standardization, and is confused with ISO 9011. The ISO 19011 standard includes the requirements for auditing a management system, and is used to train the people who certify that companies have met the requirements of standards such as ISO 9001, ISO 14001 and the like. For more information on this process, see ISO 9001 Certification.