<!ELEMENT complex (a?, (b | c | ((d|e|f|g)?, ((h|i)*, j?))))>
<!ELEMENT a EMPTY>
<!ELEMENT b EMPTY>
<!ELEMENT c EMPTY>
<!ELEMENT d EMPTY>
<!ELEMENT e EMPTY>
<!ELEMENT f EMPTY>
<!ELEMENT g EMPTY>
<!ELEMENT h EMPTY>
<!ELEMENT i EMPTY>
<!ELEMENT j EMPTY>