<p>这个怎么样?在</p>
<pre><code>html = """
<body>
<p>The prognosis of patients with rectal cancer has improved since the introduction of total mesorectal excision (TME) surgery [
<xref ref-type="bibr" rid="CR1">1</xref>&#x02013;
<xref ref-type="bibr" rid="CR3">3</xref>]. Using this surgical technique the mesorectal compartment including the rectum and perirectal fat is completely excised by sharp dissection along the mesorectal fascia (MRF) [
<xref ref-type="bibr" rid="CR1">1</xref>]. Additionally, large randomized trials have shown that neo-adjuvant therapy improves local tumor control even further, regardless of optimized surgical techniques [
<xref ref-type="bibr" rid="CR3">3</xref>,
<xref ref-type="bibr" rid="CR4">4</xref>]. The advances in rectal cancer treatment have provoked differentiated neo-adjuvant treatment strategies based on anatomical preoperative identifiable risk factors for local tumor recurrence as can be visualized with magnetic resonance imaging (MRI) [
<xref ref-type="bibr" rid="CR5">5</xref>]. One of the most important risk factors is the tumor relationship to the MRF, which actually defines the surgical circumferential resection margin (CRM) in TME surgery [
<xref ref-type="bibr" rid="CR6">6</xref>,
<xref ref-type="bibr" rid="CR7">7</xref>]. Long courses of neo-adjuvant chemoradiation have emerged as the preferential treatment of patients with anticipated tumor invasion of the MRF on MRI in order to downstage/downsize the tumor and to obtain tumor free resection margins [
<xref ref-type="bibr" rid="CR5">5</xref>].
</p>
</body>
"""
import re
re.search('<xref ref-type="bibr" rid="CR3">3</xref>(.*)', a).group(1)
</code></pre>
<p>输出为:</p>
^{pr2}$