XPath expression         |       |    PET     |   XALAN     |    LIBXML2   |   FXGREP 
                         | Nodes +-----+------+------+------+-------+------+------+----+
                         |       |  ms |    f |   ms |    f |    ms |    f |   ms |    f
-------------------------+-------+-----+------+------+------+-------+------+------+-----
//node()                 | 33806 | 238 | .079 |  100 | .008 | 18368 | .869 | 4102 | .054
//mrow[ xref]            |   750 | 158 | .054 |  120 | .010 |  3807 | .579 | 4007 | .052
//mrow[ xref]/text()     |  3162 | 161 | .054 |  190 | .015 |  5435 | .661 | 3942 | .053
//text()[../mrow[ xref]] |  3162 | 202 | .068 |  930 | .068 |  8298 | .750 |    - |    -
//*[ xref][text()]       |  2486 | 147 | .050 |  510 | .042 |  5634 | .671 | 3603 | .054
//text()/../*[ xref]     |  2486 | 175 | .059 | 1220 | .092 | 14729 | .824 |    - |    -