pos_sequence_ref_number/views/pos_template.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
<data>
    <template id="pos_sequence_ref_number_assets_backend"
              name="pos_sequence_ref_number_assets_backend"
              inherit_id="point_of_sale.assets_backend">
        <xpath expr="." position="inside">
            <script src="/pos_sequence_ref_number/static/src/js/main.js"
                    type="text/javascript"/>
            <script type="text/javascript"
                    src="/pos_sequence_ref_number/static/lib/moment.js"/>
        </xpath>
    </template>

</data>
</openerp>