pos/pos_order_to_sale_order/views/pos_order_to_sale_order.xml

<?xml version="1.0" encoding="utf-8"?>

<openerp><data>

    <template id="assets_backend" name="pos_order_to_sale_order assets" inherit_id="point_of_sale.index">
        <xpath expr="." position="inside">
            <script type="text/javascript" src="/pos_order_to_sale_order/static/src/js/pos_order_to_sale_order.js"></script>
        </xpath>
        <xpath expr="//link[@id='pos-stylesheet']" position="after">
            <link rel="stylesheet" href="/pos_order_to_sale_order/static/src/css/pos_order_to_sale_order.css"/>
        </xpath>
    </template>

</data></openerp>