@misc{ine2021imports,
  title = {Imports and Exports in Porto}
  author = {INE},
  url = {https://www.ine.pt/xportal/xmain?xpid=INE&xpgid=ine_indicadores&indOcorrCod=0008169&contexto=bd&selTab=tab2},
  year = {2021}
}