https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820%2930461-X
http://www.eca.europa.eu/Lists/ECADocuments/PRIX_LAZARO_FERNANDEZ_COMPLETE/PRIX_LAZARO_FERNANDEZ_COMPLETE_EN.PDF
http://www.cesifo-group.de/ifoHome/publications/working-papers/CESifoWP/CESifoWPdetails?wp_num=6430&CESifoWP.search=+