Some `stem:[]` blocks get exported as `dstem:[]`

Here's a source sample:
```
algebraic equation giving the number dN of particles of a non-quantized system, the components of velocity of which are comprised in the intervals (u, u + du), (v, v + dv), (w, w + dw) respectively:

where

N is the total number of particles

m is the mass of a particle

T is the thermodynamic temperature

k is the Boltzmann constant
N/N represents the probability that a particle has its components of velocity within the intervals considered.
```

Notice that `dN/N` becomes `dstem:[N]/stem:[N]`. When we capture the block of `dN/N` we need to do something... so far, `{\w}stem:[...]` really means `stem:[{\w} ...]`.