Example:
https://www.openstreetmap.org/api/0.6/way/158601617/history
returns
<osm version="0.6" generator="CGImap 0.7.0 (10448 thorn-02.openstreetmap.org)"
copyright="OpenStreetMap and contributors" attribution="http://www.openstreetmap.org/copyright"
license="http://opendatacommons.org/licenses/odbl/1-0/">
<way id="158601617" visible="true" version="1" changeset="11230310"
timestamp="2012-04-08T21:03:27Z" user="adjuva" uid="92274">
<nd ref="1707666203" />
<nd ref="1707666197" />
<nd ref="1707666196" />
<nd ref="1707666193" />
<nd ref="1707666198" />
<nd ref="1707666203" />
<tag k="description" v="HVDC converter station of the NorNet cable to norway." />
<tag k="fenced" v="yes" />
<tag k="operator" v="TenneT" />
<tag k="power" v="sub_station" />
<tag k="description" v="HVDC converter station of the NorNet cable to norway." />
<tag k="fenced" v="yes" />
<tag k="frequency" v="0;50" />
<tag k="operator" v="TenneT" />
<tag k="power" v="sub_station" />
<tag k="description" v="HVDC converter station of the NorNet cable to norway." />
<tag k="fenced" v="yes" />
...
Note the repeated tags.