Lucy, it won't work the way Marion typed it, but not because of the missing space. That space is specified in the syntax, however if it is incorrectly missing, that is something that browsers forgive (probably all, but there could be one or more that don't) and it will still work just fine and dandy. It does definitely belong there to be correct, however.
What will not work is the upper case R. To the computer, References and references are two completely different things, so there is no such tag named References, therefore it will simply be displayed on the view page exactly as it appears on the edit page or, possibly depending on the browser, it may simply not be displayed at all, since it is constructed as a tag, rather than content.