Advanced coffee reading wanted

[Dribble]

Hi All

I am a Barista trainer in South Africa and would like to increase my knowledge on both recipes and technical data. Can you recommend any books (names and author) that are regarded as a must. I have espresso 101 and Espresso perfeto.

Thanks

 

[ElPugDiablo]

Espresso Coffee by Andea Illy, Rinantonio Viani (2004). You can find it on eBay for about $70.00 before shipping cost.