Are line breaks in XML attribute values allowed?

I realise that it's not elegant or desired, but is it allowed (in well-formed XML) for an attribute value in an XML element to span multiple lines?

e.g.

<some-xml-element value="this value goes over....
multiple lines!" />

Yeah I realise there's better ways of writing that. I would personally write it like:

<some-xml-element>
<value>this value goes over...
multiple lines!</value>
</some-xml-element>

or:

<some-xml-element value="this value goes over....&#13;&#10;" />

But we have our own XML parser and I'd like to know whether the first example is allowed in well-formed XML.