Is that problem for awk?

Hi,

I have the following problem. In my text-file each line has the
following format:

field_1 field_2 ... field_n (tf. field_1a, field_2a ... field_ka)

And I need to extract field_1a, field_2a, ...and field_ka. Here I see
several subproblems which I cannot solve:
1. Different lines have different number of fields before the
(tf. ... ) block.
2. (tf. ... ) blocks also contain different number of fields.
3. There is no space between "field_ka" and ")". And I want to remove
")".

Can this problem be easily solved in awk?

Thank you.