View source for Talk:Ordinary differential equations, property C for

==Perpetuation of misprints==
Comparison with the printed text shows that the square in the first equation $\square _ { m } u = \dots$ should be an $\ell$, having presumably been replaced by a visible space at some point in the initial TeX-ification.  Similarly the text letter $\text{l}$, indistinguishable from a digit $1$, subsequently should also be an $\ell$.

I believe that there's a misprint in the original printed test, though, where there are two coccurrences of a function $\phi_m$, the second of which I suggest is $\psi_m$.  [[User:Richard Pinch|Richard Pinch]] ([[User talk:Richard Pinch|talk]]) 10:12, 13 January 2021 (UTC)