Circular Dependency! object creation

The Code is very simple! I have two classes student.h and diciplina.h and I need to maintain a circular dependency between them!

When I'm in student.h I can create an attribute of class discipline use new, constructor, sets and gets. But when I do, I can create and set to 0 but n can give a new one and use: /

[Error] forward declaration of 'class discipline: student' and
[Error] invalid use of incomplete type 'class diciplina :: student'

You're already grateful!

#ifndef DICIPLINA_H
#define DICIPLINA_H

#include <string>
using namespace std;
#include "aluno.h"

#define MAX 20


class aluno;

class diciplina{

    public:

    class aluno;

    diciplina(string codDic,    string descricaoDisc){  

    this->codDic = codDic;
    this->descricaoDisc = descricaoDisc;

    for(int i = 0; i<20; i++) // Inicializa com tudo 0
    dA[i] = 0;  
    }

    ~diciplina(){

    delete[]dA;

    }   
    bool matricula(aluno **al,int id){

    for(int i = 0; i<10; i++)
    if(dA[i] == 0){
    dA[i] = new aluno("Fulano","09834534","Computer Science"); //  ESSA LINHA QUE DA ERRO
    return true;
    system("pause");
    }
    return false;   
    }

    private:
    string codDic;
    string descricaoDisc;
    aluno *dA[MAX];


    };  
#endif

    #ifndef ALUNO_H
#define ALUNO_H
#include <string>
#include <iostream>
#include "diciplina.h"

using namespace std;

class diciplina; // declaracação forward

class aluno
{
    public:

        aluno(string nome, string cpf, string curso){
        this->nome = nome;
        this->cpf = cpf;
        this->curso = curso;    

        for(int i = 0; i<10; i++)
        alunoDiciplinas[i] = 0;
        }
        ~aluno(){       

        delete[] alunoDiciplinas;

        }

        bool matricula(diciplina **dic,int id){

        for(int i = 0; i<10; i++)
        if(alunoDiciplinas[i] == 0){
        alunoDiciplinas[i] = new diciplina(dic[id]->getCod(),dic[id]-   >getDiciplina()); // MAS AQUI NÃO DA ERRO !!
        return true;
        }
        return false;
    }



        private:        
        string nome, cpf, curso;
        diciplina *alunoDiciplinas[10];

};
#endif