Source: https://www.researchgate.net/profile/Faiz_Gallouj/publication/280681932_Business_Cycles_and_Service_Innovations_Some_Questions_in_the_Light_of_Schumpeterian_Thought/links/56091ca408ae13969149c6f6/Business-Cycles-and-Service-Innovations-Some-Questions-in-the-Light-of-Schumpeterian-Thought.pdf