Skype

https://www.lync.se/2019/12/native-federation-for-11-chats/

https://techcommunity.microsoft.com/t5/Microsoft-Teams-Blog/Meetings-First-brings-Microsoft-Teams-meetings-to-Skype-for/ba-p/828340

Skype for Business and Teams features comparison table  

https://techcommunity.microsoft.com/t5/Microsoft-Teams-Blog/Skype-for-Business-Online-to-Be-Retired-in-2021/ba-p/777833

https://erwinbierens.com/post/2019-04-18-get-the-hell-out-of-islandsmode/

In Teams Only, Skype for Business always prompts Join Meeting Audio choice

Scheduling a Skype for Business Meeting in Teams Only Mode with Skype for Business Web Scheduler

https://lucavitali.wordpress.com/2017/10/01/sfb-teams-features-comparison-table/amp/

What is the date customers have to move from Skype for Business to Microsoft Teams?

https://techcommunity.microsoft.com/t5/Microsoft-Teams-Blog/Introducing-Microsoft-Teams-Rooms/ba-p/323848

https://erwinbierens.com/skype-for-business-and-microsoft-teams-network-testing/