<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>18950</termId><termName>aortic valve</termName><termType>PT</termType><termCreatedDate>0000-00-00 00:00:00</termCreatedDate><relation><relationType>BT</relationType><termId>18948</termId><termName>heart valves</termName><termType>PT</termType></relation><relation><relationType>RT</relationType><termId>18952</termId><termName>aorta</termName><termType>PT</termType></relation></term>  </Zthes>