The schema for MathML3 is included in the Relax NG and Relax NG compact syntax versions of focheck.
The MathML3 schema was downloaded from http://www.w3.org/Math/RelaxNG/
# This is the Mathematical Markup Language (MathML) 3.0, an XML
# application for describing mathematical notation and capturing
# both its structure and content.
#
# Copyright 1998-2010 W3C (MIT, ERCIM, Keio)
#
# Use and distribution of this code are permitted under the terms
# W3C Software Notice and License
# http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231