Historical FreeBSD ISOs ?

[Pierre DAVID]

Hi,

for a study, I need ISO images for historical versions of FreeBSD,
such as 3.5-RELEASE, 4.11-RELEASE, and so on (i386 and/or amd64).

I searched on ftp.freebsd.org, but the oldest one is 11.2-RELEASE.

Do you know if such ISO images are available somewhere? Or must I
install those systems from source?

Thanks in advance,

Pierre David