Extracting the only one element from xml

[Dhruba Mahanta]

I used the following statements,
INSERT INTO x VALUES
('
<book>
<title>A guide to the SQL standard</title>
<author>
<initial>Dhruba</initial>
<surname>Mahanta</surname>
</author>
</book>
');

and

INSERT INTO x VALUES
('
<book>
<title>A guide to the SQL standard</title>
<author>
<initial>Debojit</initial>
<surname>Saikia</surname>
</author>
</book>
');
Now how can I display only 'Dhruba' and 'Mahanta' by using mysql statements from what I have entered in database. Please help.