1. Scenario Mobile Communications 2010: Study on Forecast Development and Future Trends in Technical Development and Commercial Provision up to the Year 2010;Eutelis;Report to the Commission of the European Communities,1993
2. Data updated to April 1994
3. The Economics of Industrial Innovation;Freeman,1982
4. Global Competitiveness of US Advanced-Technology Industries: Cellular Communications;US International Trade Commission,1993