Nakamura, Leonard I. (FRB); Samuels, Jon (BEA); Soloveichik, Rachel H. (BEA). "Measuring the "Free" Digital Economy Within the GDP and Productivity Accounts"(PDF). SSRN.com. Social Science Research Network publishing working paper 17-37 of the Research Department, Federal Reserve Bank of Philadelphia. October 24, 2017. səh. 37 (Fig. 3). March 20, 2021 tarixində arxivləşdirilib(PDF).
Nakamura, Leonard I. (FRB); Samuels, Jon (BEA); Soloveichik, Rachel H. (BEA). "Measuring the "Free" Digital Economy Within the GDP and Productivity Accounts"(PDF). SSRN.com. Social Science Research Network publishing working paper 17-37 of the Research Department, Federal Reserve Bank of Philadelphia. October 24, 2017. səh. 37 (Fig. 3). March 20, 2021 tarixində arxivləşdirilib(PDF).