Link Opengl in a Dll project

I’m trying to create my first 2d game engine. It would be a set of libraries that give me more efficiency and handiness to develop 2d games. Unfortunately it gives me linking error while I compile.I check if I’ve linked fine the libraries and, why not, if the libraries exists but I can’t find the solution.
Here’s the errors (it’s in italian, sorry):

# Erorre = error
# simbolo esterno = external symbol
# non risolto = unresolved

Errore	1	error LNK2001: simbolo esterno ___glewAttachShader non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	2	error LNK2001: simbolo esterno ___glewCompileShader non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	3	error LNK2001: simbolo esterno ___glewCreateProgram non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	4	error LNK2001: simbolo esterno ___glewCreateShader non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	5	error LNK2001: simbolo esterno ___glewDeleteProgram non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	6	error LNK2001: simbolo esterno ___glewDeleteShader non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	7	error LNK2001: simbolo esterno ___glewDetachShader non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	8	error LNK2001: simbolo esterno ___glewLinkProgram non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	9	error LNK2001: simbolo esterno ___glewShaderSource non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll
Errore	10	error LNK2001: simbolo esterno ___glewUseProgram non risolto	C:\Users\Lorenzo\Documents\Visual Studio 2013\Projects\Engine\EngineDll\Graphics.obj	EngineDll

And the header file that I’m trying to compile:

#include <GL\glew.h>
#include <glm\glm.hpp>

#define DLLEXPORT __declspec(dllexport)
#define DLLIMPORT __declspec(dllimport)

namespace gr
{
	struct Color
	{
	private:
		glm::vec3 color;

	public:
        Color(glm::vec3 color) : color(color) {}
		~Color() {}

		DLLEXPORT GLfloat operator[](unsigned char i) { return color[i]; }
	};

    struct Shader
    {
    private:
        GLuint program, shaders[2];

    public:
        Shader();
        ~Shader();

        void use();
    };

    class Drawable
    {
    protected:
        GLfloat x, y, z;

    public:
        Drawable(GLfloat x, GLfloat y, GLfloat z) : x(x), y(y), z(z) {}
        ~Drawable() {}

        virtual void Render() = NULL;
    };

    class Rectangle : public Drawable
    {
    private:
        GLfloat width, height;
        Color color;

    public:
        Rectangle(GLfloat x, GLfloat y, GLfloat z, GLfloat width, GLfloat height, Color color) : Drawable(x, y, z), width(width), height(height), color(color) {}
        ~Rectangle() {}

        void Render();
    };
}

P.S: My project is for Windows x64 and I don’t use precompiled headers!

Anyone know how can I resolve?

Maybe, I have to init all function with __declspec(dllimport)?

Something like:

__declspec(dllimport) GLuint glCreateShader(GLenum);

/// call shader function

Here’s the cpp where I called OpenGL functions:

#include "Graphics.hpp"

static const GLchar *shaderSources[2] =
{
    {
        "void main()"
        "{"
        "gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;"
        "}"
    },
    {
        "void main()"
        "{"
        "gl_FragColor = gl_Color;"
        "}"
    }
};

static GLuint createShader(const GLchar *source, GLenum type)
{
    GLuint shader = glCreateShader(type);
    glShaderSource(shader, 1, &source, NULL);
    glCompileShader(shader);

    return shader;
}

gr::Shader::Shader()
{
    program = glCreateProgram();

    for (unsigned short i = 0; i < 2; i++)
    {
        shaders[i] = createShader(shaderSources[i], 0x4B31 - i);
        glAttachShader(program, shaders[i]);
    }
    
    glLinkProgram(program);
}

gr::Shader::~Shader()
{
    for (unsigned short i = 0; i < 2; i++)
    {
        glDetachShader(program, shaders[i]);
        glDeleteShader(shaders[i]);
    }

    glDeleteProgram(program);
}

void gr::Shader::use()
{
    glUseProgram(program);
}