  This note discusses three examples given in the recent technical
correspondence paper [1], which addresses the results presented in [2,3,4]. It
is shown that the first example ([1], Section 3) is irrelevant to the results
of [2]. The second example ([1], Section 4) establishes a well-known fact that
a continuous differentiator can exactly differentiate a signal, only if its
second derivative is equal zero. This note provides a method to extend the
algorithms presented in [3] to the general case. Finally, the third example
([1], Section 5) presents a particular case related to Theorem 1 of [4].
Theorem 1 of [4] remains, however, valid in the most practical case of
selecting control gains. The result of Theorem 2 in [4] estimating the fixed
convergence time holds as well.
