Sharkovsky’s Theorem. A direct proof and further observations.

We present a proof by Keith Burns and Boris Hasselblatt for Sharkovsky’s famous theorem regarding possible sets of periods for interval maps. Their proof improves the former proof through the introduction of Štefan sequences. Furthermore we present some observations on the family of truncated tent maps, which are used by Burns and Hasselblatt to prove the Sharkovsky realization theorem.