The Unicode catalogue includes a number of white-space characters, some of which don't appear to work in *any* context in HTML documents - but some of which, rather usefully, do.

Here is an example:

```html
<h1 title="Hi! As a title attribute, &#013;I can contain &#009;&#009;horizontal tabs &#013;and carriage returns &#010;and line feeds.">HTML's handling of &amp;009; | &amp;010; | &amp;013;</h1>

<p>Hello. As a paragraph element, I can't contain &#009;horizontal tabs &#013;or carriage returns &#010;or line feeds.</p>

<input type="submit" value="I am a value attribute and &#010;like title I can also handle line feeds" /><br />

<input type="submit" value="I am another value attribute. &#009;&#009;Like title I can handle horizontal tabs" /><br />

<input type="submit" value="I am a third value attribute. &#013;Unlike title I can't handle carriage returns" />
```

Is there any official spec or series of guidelines which detail which white-space characters can be deployed in HTML documents and where?