@misc{ine2020gva,
  title = {GVA by economic activity - Porto}
  author = {INE},
  url = {https://www.ine.pt/xportal/xmain?xpid=INE&xpgid=ine_indicadores&indOcorrCod=0008513&contexto=bd&selTab=tab2},
  year = {2020}
}