I am not 100% sure of the meaning of these terms.
Is a business process a flow in an application? (e.g. creating an invoice)
Are business rules parts of a business process? and, are business processes part of the business logic?
A business process is a series of actions that are executed by a business to perform a particular task. For example, when a customer places an order with a company that company goes through a process that might involve checking stock in the warehouse and getting the item from the warehouse, packaging the item, sending it and finally invoicing it.
A business rule is a requirement in the business. For example, a customer placing an order must provide a valid credit card number in order to be able to place that order. Business rules have very little to do with software: they are simply requirements of a real-world process.
The business logic deals with enforcing business rules in a software system. When placing an order, the business logic to validate credit card numbers is invoked in order to enforce the business rule that all orders require a valid credit card number.