The RESTful principle actually just declares that request response cycles and server-client interactions don't have to be stateful, not that it's necessary they're stateless.
It's still possible to use sessions and other ways of maintaining client state while adhering to other stateless principles such as indempotency of certains types of requests.
It's still possible to use sessions and other ways of maintaining client state while adhering to other stateless principles such as indempotency of certains types of requests.