CZJ Tessar 50mm f/2.8 disassemble|Need help?|

[Saki3d]

Hello friends,
i was have some particles inside lenses and i find this link
http://oomz.net/tessar/
and started to disassemble parts
but i am stuck at front lens part,

in this picture the number25 one i can not unscrew it.



i tried too many way but it is not moving any milimeters
is there any tool to unscrew it, rear lens have places to unscrew it with tool but this one don't.

i need to clean between "middle lens" and "front lens"

hope to get some support here~

thanks
Serkan.