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TPS55010: Transformer design: can I use core without air gap??

Part Number: TPS55010

I need 2 power supply: one with +-5V output and current less than 10mA and second for +-35V and current less than 10mA.
I do not want use WE transformer, because for turn ratio 1:8:8, output voltage is too low (for +-35V) or to high (more than 7,2V).
I want make my own design. I want use core transformer EP7 like this:

but i do not know if i must to use core with air gap or without.
Can I use core without air gap??