pos_buttons/views/templates.xml

<openerp>
    <data>
        <template id="pos_buttons.eiru_assets" name="pos_buttons_assets" inherit_id="eiru_assets.assets">
            <xpath expr="." position="inside">
                <link rel="stylesheet" href="/pos_buttons/static/src/css/style.css"/>
                <script type="text/javascript" src="/pos_buttons/static/src/js/pos_buttons.js"/>
                <script type="text/javascript" src="/pos_buttons/static/src/js/purchases_buttons.js"/>
            </xpath>
        </template>
    </data>
</openerp>