I have a B.Sc. and an M.Sc., both in Applied Mathematics.

English isn’t my first language.

I do read English decently, though.

Let $x=[a, b, c, d, \ldots]^{\mathrm T}$. Then one obvious modal matrix for the rank-1 matrix $xx^{\mathrm T}$ is $$\begin{bmatrix} \def\p{\!\!+\!} a & -b^2a & -c^2a & -d^2a & \ldots \\ b & a^2b & -c^2b & -d^2b & \\ c & & (a^2\p b^2)c & -d^2c \\ d & & & (a^2\p b^2\p c^2)d \\ \vdots & & & &\ddots \end{bmatrix}$$