<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31333776</termId><termName>hyperboloid</termName><termType>PT</termType><termNote><![CDATA[ Shape comprising the open surface generated by revolving a hyperbola about either of its axes. If the tranverse axis of the surface lies along the x axis and its centre lies at the origin and if a, b, and c are the principal semi-axes, then the general equation of the surface is expressed as x2/a2 ± y2/b2 − z2/c2 = 1. ]]></termNote><termCreatedDate>2026-03-30 20:29:57</termCreatedDate><relation><relationType>BT</relationType><termId>31311876</termId><termName>geometric shape</termName><termType>PT</termType></relation></term>  </Zthes>