 			else
 				closingHTML = "</math></div>"
 
-			return html + "<mrow>" + @children.map((child) -> child.toMathML()).join("<mo>+</mo>") + "</mrow>" + closingHTML
+			return html + "<mrow>" + @children.map((child) -> "<mfenced>" + child.toMathML() + "<mfenced>").join("<mo>+</mo>") + "</mrow>" + closingHTML
 
 		toHTML: (equationID, expression=false, equality="0", topLevel=false) ->
 			# Return an HTML string representing this node.

			else if @children.right.evaluate?() == 0
				return html + "<mn>1</mn>" + closingHTML
			else
				innerHTML = "#{@children.left.toMathML()}#{@children.right.toMathML()}"
				innerHTML = "<msup>#{innerHTML}</msup>"
				if @children.right.evaluate?() < 0
					right = @children.right.copy()
					right = Mul("-1", right)
					right = right.simplify()
					innerHTML = "<mfrac><mn>1</mn>#{innerHTML}</mfrac>"
				return html + innerHTML + closingHTML

			else
				closingHTML = "</div>"

			return html + @children.map((child) -> "(" + child.toHTML() + ")").join("&cdot;") + closingHTML

		toLaTeX: ->
			# Return a LaTeX string representing this node.
			return @children.map((child) -> "\\left(" + child.toLaTeX() + "\\right)").join("\\cdot")

	class Pow extends nodes.BinaryNode
		# Represent powers.
