On Friday 2018-03-02, I installed a couple of distros side by side in VMs.
I used the latest available installation image for each. Well, AFAIK. Everything in this document is AFAIK.
ISO: nixos-minimal--18.03pre129076.831ef4756e3-x86_64-linux.iso DOC: https://nixos.org/nixos/manual/index.html#sec-installation
ISO: guixsd-install-0.14.0.x86_64-linux.iso DOC: https://www.gnu.org/software/guix/manual/html_node/Preparing-for-Installation.html#Preparing-for-Installation