http://plethon.eu/feature-tour/feature-three/
https://reasonstreet.co/business-model-professional-services/
https://www.godaddy.com/garage/using-a-lean-canvas-to-create-your-business-plan/
https://www.transentis.com/a-business-model-blueprint-for-professional-service-firms-value-network/
http://durichitayat.net/business-model-for-the-professional-service-firm/
https://medium.com/swlh/the-two-laws-of-building-products-74880772c678