Intercompany across LE and BU

Summary

Document and/or pointers for intercompany transfers across LE and BU

Content

Experts,

Looking for a document or pointer on Intercompany across LE and BU. All the IMT related documents that I came across are for material transfer within BU/LE. So there is no intercompany AR/AP generation. 

Looking for detailed document on setup, transfer pricing and process to generate intercompany AR/AP invoice after shipment from one warehouse (belonging to one BU/LE) to another warehouse (belonging to another BU/LE)

Thanks