<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31305977</termId><termName>tracer</termName><termType>PT</termType><termNote><![CDATA[ Substance which is traced through a biological, chemical, or physical system in order to study the system. ]]></termNote><termCreatedDate>2026-03-30 20:22:19</termCreatedDate><relation><relationType>BT</relationType><termId>31298939</termId><termName>materials by function</termName><termType>PT</termType></relation></term>  </Zthes>