Queue and stack based on linked list (C++)

Queue.h

/**
	Queue.h
	Implements a class template of a queue
	abstract data type.

	@author Sam Griffiths
	www.computist.xyz
*/

#pragma once

#include "DESLinkedList.h"

template <typename T>
class Queue : protected DESLinkedList<T>
{
public:
	using DESLinkedList<T>::empty;

	//Enqueues the given element
	void enqueue(const T &elt)
	{
		this->add(elt, this->BACK);
	}

	//Dequeues the next element
	void dequeue()
	{
		this->remove(this->FRONT);
	}

	//Returns the next element
	T &peek()
	{
		return DESLinkedList<T>::peek(this->FRONT);
	}
	
	//Outputs the queue to the stream
	friend std::ostream& operator<<(std::ostream &os, const Queue &q)
	{
		return os << static_cast<const DESLinkedList<T> &>(q);
	}
};

Stack.h

template <typename T>
class Stack : protected DESLinkedList<T>
{
public:
	using DESLinkedList<T>::empty;

	//Pushes the given element
	void push(const T &elt)
	{
		this->add(elt, this->FRONT);
	}

	//Pops the next element
	void pop()
	{
		this->remove(this->FRONT);
	}

	//Returns the next element
	T &peek()
	{
		return DESLinkedList<T>::peek(this->FRONT);
	}

	//Outputs the stack to the stream
	friend std::ostream& operator<<(std::ostream &os, const Stack &q)
	{
		return os << static_cast<const DESLinkedList<T> &>(q);
	}
};