Σακκάς, Δ. Α., Σπυροπούλου, ΄. Σ., Σπυροπούλου, Έ. Σ., Δρουκόπουλος, Β., Spyropoulou, E. S., Σπυροπούλου, Ε. Σ., & Σπυροπούλου, Ε. Σ. (1995). The European observatory for small and medium-sized enterprises: Research environment and innovation in greek manufacturing. Athens: Centre of Planning and Economic Research.

Σακκάς, Δημήτριος Α., ΄Ελενα Σ Σπυροπούλου, Έλενα Σ Σπυροπούλου, Βασίλης Δρουκόπουλος, Elena S. Spyropoulou, Ελενα Σ Σπυροπούλου, and Ελενα Σ Σπυροπούλου. The European Observatory for Small and Medium-sized Enterprises: Research Environment and Innovation in Greek Manufacturing. Athens: Centre of Planning and Economic Research, 1995.

Σακκάς, Δημήτριος Α., et al. The European Observatory for Small and Medium-sized Enterprises: Research Environment and Innovation in Greek Manufacturing. Athens: Centre of Planning and Economic Research, 1995.