Nodes in the final sequences appear in document order

      <xsl:stylesheet
                  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                  version="2.0">
            <xsl:output  method="xml"
                        indent="yes"
                        omit-xml-declaration="yes"/>

            <xsl:template  match="/aaa">
                  <xxx>
                        <xsl:value-of  select="bbb | ccc"/>
                  </xxx>
                  <yyy>
                        <xsl:value-of  select="ccc | bbb"/>
                  </yyy>
            </xsl:template>

      </xsl:stylesheet>

      <aaa>
            <bbb>B1</bbb>
            <bbb>B2</bbb>
            <ccc>C1</ccc>
            <ccc>C2</ccc>
      </aaa>

      <xxx>B1 B2 C1 C2</xxx>
      <yyy>B1 B2 C1 C2</yyy>