| Authors | Title | Country(ies) | Years | Data Sources | Sample | Dependent Variable | Independent variable | Econometric model |
| | Patents as quality signals? The implications for financing constraints on R & D | Belgium | 2000-2009 | Flemish R & D Survey, OECD/EPO database, Bureau van Dijk BEL-FIRST database | 4390 Firms | R & D Intensity | Patent Applications | Tobit |
| | Does Access to Finance Enhance SME Innovation and Productivity in Nigeria? Evidence from the World Bank Enterprise Survey | Nigeria | Not mentioned | World Bank Enterprise Survey | 2127 Firms | Conduct of R & D | Internal finance, External finance, Access to bank finance, Financial constraints | Logit |
| | Access to finance and innovative activity of EU firms: A cluster analysis | Europe | 2015 | Survey of European Investment Bank | 9067 Firms | Conduct of R & D, R & D Intensity | Clusters of Financing Sources | Logit |
| | Financial constraints, government support, and firm innovation: empirical evidence from developing countries | Global | 2006-2017 | World Bank Enterprise & Innovation Surveys | 71,450 Firms | Conduct of R & D | Difficulty of access in external capital | Instumental Variable Probit |