Problems with making a contact sheet of old/uncut film

I have come across 20 rolls of old 35mm film (kodak panatomic). They were developed a long time ago and have been kept in an old Leica film holder. The problem is they cannot be cut and loaded into film sheets because they have been rolled up for so long. How can they be flattened, safely, so they can then be cut and loaded into negative sheets?

Unroll and flatten? Cut, load into film sheets and then flatten under some books?

Attached are two photos so you can see what I'm talking about.

Thanks for any help or suggestions,
Sean

In my experience that film will not flatten even if you rewash it all. If it was me, I would get a small sheet of quarter inch plate glass and tape strips down with scotch tape and then lay the glass on printing paper to make contacts. It will not be easy and you won't be able to get a whole rolls worth on one sheet of paper but you will get them contacted. Then you put them in film sleeves in a binder. Anyway that is what I would do.

I'm with @dpurdy I don't think those will uncurl during this geological era.

Cutting them into strips and archiving shouldn't be too difficult, and taping them to glass will let you contact print them. That's about all you can reasonably do.