Denis Simonov is the author of Firebird documentation, seasoned developer and DBA.

Denis Simonov sells the following books and courses in FirebirdSQL shop:

1 . Book: Detailed new features of Firebird 5, 2nd edition (available in English, Portuguese, German, Polish, Russian, and more)

2. Book:  Secrets of Firebird Query Optimizer  (available in English, Portuguese, German)