António Marques and  Graça Guedes,  Innovation in “Low-Tech” Industries: Portuguese Footwear Industry.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2015, vol. 105(9). 3195 - 3199
    [viewed 20 April 2024]. Available from: https://publications.waset.org/pdf/10002529.