F. M. Matos et al.,  "Intellectual capital and innovation for sustainable smart cities: The case of N-Tuple of Helices", in Intellectual capital management as a driver of sustainability: Perspectives for organizations and society, Matos, F. and Vairinhos, V. and Selig, P. M. and Edvinsson, L., Ed., Springer, 2019, pp. 49-66