The sequence for the following business transactions and documents for external activities in a project is vendor selection -> purchase order creation -> service entry sheet creation -> service entry sheet approval. Vendor selection is a process that involves choosing a suitable vendor for providing external services for a project activity. Purchase order creation is an action that involves creating a document that contains the details of the service request and sending it to the vendor. Service entry sheet creation is an action that involves creating a document that records the delivery of services from the vendor and posting actual costs to the project. Service entry sheet approval is an action that involves checking and confirming the accuracy of the service entry sheet before paying the vendor. Reference: https://help.sap.com/doc/0f069b2e08b748f1b480d4c8b46c3c49/100/en-US/6a7a9f0a6e421014e10000000a174cb4.html