Table 1: the upper-bound 30 for μ_2(1,10) should be read instead for μ_2(2,5). Table 1: the correct upper-bound for μ_2(1,10) should be 31 (as reported in "Multiplication of polynomials modulo x^n" by Cenk & Özbudak 2011) Table 2: the justification displayed for the value μ_2(1,10) should be read instead for μ_2(2,5) Table 2: see thesis Appendix §2 for the formulas justifying the new exact values of μ(2,3), μ(2,4) and μ(2,5) Observation 4: it turned out this was already known to BDEZ as unpublished material: see their slides, and the work of Svyatoslav Covanov 2018. Lemma 7 & Proposition 8: they also turned out to be already known, to Hugues Randriam. §4.1 ---> see VII.4.1 of thesis instead, for more precise statements