Correction (3e ligne) : « d 3 S d x d z 3 {\displaystyle {\frac {\operatorname {d} ^{3}S}{\operatorname {d} x\operatorname {d} z^{3}}}} » → « d 3 S d x d z 2 {\displaystyle {\frac {\operatorname {d} ^{3}S}{\operatorname {d} x\operatorname {d} z^{2}}}} » (coquille)
