  Omega-limit sets play an important role in one-dimensional dynamics. During
last fifty year at least three definitions of basic set has appeared. Authors
often use results with different definition. Here we fill in the gap of missing
proof of equivalency of these definitions.
  Using results on basic sets we generalize results in paper [P.~Oprocha,
Invariant scrambled sets and distributional chaos, Dyn. Syst. 24 (2009), no. 1,
31--43.] to the case continuous maps of finite graphs. The Li-Yorke chaos is
weaker than positive topological entropy. The equivalency arises when we add
condition of invariance to Li-Yorke scrambled set.
  In this note we show that for a continuous graph map properties positive
topological entropy; horseshoe; invariant Li-Yorke scrambled set; uniform
invariant distributional chaotic scrambled set and distributionaly chaotic pair
are mutually equivalent.
