EPD formatI made an epd file of 3710 positions that occurred after 8 moves (16 plies) in high level human games. Each position is unique and occurred at least 10 times in my databases (289,000 games).
This epd opening book is a neutral book and is suitable for use in a GUI that enables epd files to be used as opening books. Arena is one such GUI. I am not familiar with other GUIs so I do not know if they can handle an epd book.