Multi-fluid cosmology in Einstein gravity: analytical solutions
  We review analytical solutions of the Einstein equations which are expressed
in terms of elementary functions and describe
Friedmann-Lema\^itre-Robertson-Walker universes sourced by multiple (real or
effective) perfect fluids with constant equations of state. Effective fluids
include spatial curvature, the cosmological constant, and scalar fields. We
provide a description with unified notation, explicit and parametric forms of
the solutions, and relations between different expressions present in the
literature. Interesting solutions from a modern point of view include
interacting fluids and scalar fields. Old solutions, integrability conditions,
and solution methods keep being rediscovered, which motivates a review with
modern eyes.
