The article titled “A Review on the Control of Second Order Underactuated Mechanical Systems” [1] was found to contain material from published work, which was not cited. The earlier article is as follows:

Yang Liu and Hongnian Yu, “A survey of underactuated mechanical systems,” IET Control Theory & Applications, vol. 7, no. 7, pp. 921–935, 2 May 2013, doi: 10.1049/ietcta. 2012.0505 [2].

Figures 1–6 are conceptually the same as Figures 1–4 and 5–7, respectively. Table 1, showing the equations of motion for underactuated mechanical systems, is the same as Table 1 in the earlier article. The same eight examples of underactuated systems are shown in Section 2 and Section 2.2 in the earlier article. Section 3 and Section 2.1 are similar, and the titles of Sections 4 and 5 versus Sections 3 and 4 are the same: “Classification of Underactuated Mechanical Systems” and “Control of Underactuated Mechanical Systems” versus “Classification of UMS” and “Control of UMS.” The contents of Section 5 in both articles are similar, and Section 6.1 on “Intelligent Controller (Fuzzy Logic)” is similar to Section 4.4 on “Fuzzy Control” in the earlier article.

The authors apologize for this.