Corrigendum to: “On ordering free groups” [J. Symbolic Comput. 40 (2005) 1285–1290]

The proof of the main result of the paper is corrected.     

Corrigendum to “Uniform constant-depth threshold circuits for division and iterated multiplication” [J. Comput. System Sci. 65 (4) (2002) 695–716]

In this corrigendum, we retract part of our Corollary 6.6, which was presented as an immediate and obvious consequence of our main theorem, which showed that division lies in Dlogtime-uniform TC⁰${\mathrm{TC}}^0$.     

Comments on “Wirtinger-based integral inequality: Application to time-delay systems [Automatica 49 (2013) 2860–2866]”

In a recent paper (Automatica 49 (2013) 2860–2866), the Wirtinger-based inequality has been introduced to derive tractable stability conditions for time-delay or sampled-data systems. We point out that there exist two errors in Theorem 8 for the stability analysis of sampled-data systems, and the correct theorem is presented.     

Comment on “On LMI conditions to design observer-based controllers for linear systems with parameter uncertainties [Automatica 49 (2013) 3700–3704]”

The main objective of this note is to point out the fatal error in a recent paper (Automatica 49 (2013) 3700–3704) and present a correct result. One numerical example is also given in order to show the nonsuperiority of the aforementioned paper to the existing literatures.