There’s an updated (May 2019) Dynamics 365 Business Central Licensing Guide with three main changes.
Firstly, there’s wording added on page 4 to confirm that there are no minimum licence purchase requirements, and that Essentials and Premium licences may not be mixed.
Then on page 5 there’s a link included to a document which gives further information on how the Team Members licence works in Business Central.
And finally, page 6 sees the addition of text confirming that Business Central includes three External Accountant licences.
Find this guide here: http://bit.ly/MSLicensingGuides.