I found some recomendations by testing a PB installation
https://developers.google.com/speed/pagespeed/insights/?hl=es&url=http%3A%2F%2Fpb.default.books4languages.com%2Fbook-test%2Ffront-matter%2Fintroduction%2F&tab=mobile
I found some recomendations by testing a PB installation
https://developers.google.com/speed/pagespeed/insights/?hl=es&url=http%3A%2F%2Fpb.default.books4languages.com%2Fbook-test%2Ffront-matter%2Fintroduction%2F&tab=mobile