There are a number of apparently unnecessary inconsistencies between [template.slice.array.overview], [template.gslice.array.overview], [template.mask.array.overview], and [template.indirect.array.overview].

[template.slice.array.overview] p1 says:

The slice_array template is a helper template used by the slice subscript operator

slice_array<T> valarray<T>::operator[](slice);

And [template.gslice.array.overview] p1 says:

This template is a helper template used by the slice subscript operator

gslice_array<T> valarray<T>::operator[](const gslice&);

Either the latter should say "gslice subscript operator" or the word slice should not be in code font (which would be consistent with "mask subscript operator" and "indirect subscript operator" in [template.mask.array.overview] and [template.indirect.array.overview] respectively).

Also [template.slice.array.overview] p1 says "The slice_array template is a helper template" but the other three helpers say "This template is a helper template". Presumably they could be consistent.

The "It has reference semantics ..." wording is part of p1 in [template.slice.array.overview] but is a separate paragraph p2 in the other three places.

The explanation of the effects ("the expression ... has the effect of ...") is an Example: in [template.slice.array.overview], its own paragraph in [template.gslice.array.overview], and part of p2 in [template.mask.array.overview] and [template.indirect.array.overview].