operator: Internet Archive Internet Archive ID: birdsEuropeIIGoul described at URL: https://archive.org/download/birdsEuropeIIGoul/birdsEuropeIIGoul.pdf...
Internet Archive ID: BirdsAsiaJohnGoIIGoul described at URL: https://archive.org/download/BirdsAsiaJohnGoIIGoul/BirdsAsiaJohnGoIIGoul.pdf determination method...