$$ \def\ivet{\boldsymbol{i}} \def\jvet{\boldsymbol{j}} \def\kvet{\boldsymbol{k}} \def\avet{\boldsymbol{a}} \def\bvet{\boldsymbol{b}} \def\cvet{\boldsymbol{c}} \def\fvet{\boldsymbol{f}} \def\ovet{\boldsymbol{o}} \def\pvet{\boldsymbol{p}} \def\tvet{\boldsymbol{t}} \def\uvet{\boldsymbol{u}} \def\vvet{\boldsymbol{v}} \def\omvet{\boldsymbol{\omega}} \def\tauvet{\boldsymbol{\tau}} \def\Ivet{\boldsymbol{I}} \def\Mvet{\boldsymbol{M}} \def\Rvet{\boldsymbol{R}} \def\calK{\mathcal{K}} \def\calP{\mathcal{P}} \def\calR{\mathcal{R}} \def\de{\textrm{d}} \def\T{^{\sf T}} $$