<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31344873</termId><termName>hydrogen</termName><termType>PT</termType><termNote><![CDATA[ Nonmetallic chemical element (H). It is a colorless, odorless, tasteless gas, the lightest chemical element, and is used in rocket fuels and balloons. Its most important compound (with oxygen) is water. ]]></termNote><termCreatedDate>2026-03-30 20:33:01</termCreatedDate><relation><relationType>UF</relationType><termId>31344874</termId><termName>H</termName><termType>ND</termType></relation><relation><relationType>BT</relationType><termId>31320551</termId><termName>hydrogen and hydrogen isotopes</termName><termType>PT</termType></relation></term>  </Zthes>