} else if(tag.equals(MathExpressionGeneric.TAG)) {
express = new MathExpressionGeneric(element,
cf.getChildContext(MathExpressionGeneric.GROUP));
} else if(tag.equals(MathExpressionConditionBinary.TAG)) {
express = new MathExpressionConditionBinary(element,
cf.getChildContext(MathExpressionConditionBinary.GROUP));
} else if(tag.equals(MathExpressionConditionUnaryNull.TAG)) {
express = new MathExpressionConditionUnaryNull(element,
cf.getChildContext(MathExpressionConditionUnaryNull.GROUP));