XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (297 page)

As operators are tokens, they may always be preceded and followed by whitespace, and must not include any embedded whitespace. In some cases it is necessary to precede or follow an operator by whitespace to ensure it is recognized. This applies not only to the named operators (such as
and
and
or
) but also to the minus sign
–
, which could be mistaken for a hyphen if written with no preceding space.

The numeric comparison operators are written here as XPath sees them; when they appear in an XSLT stylesheet, the special characters
<
and
>
should be written
<
and
>
, respectively.