bool Album::operator==(Album &album) {
    return this->titel == album.titel;
}

bool Album::operator<(Album &album) {
    return this->titel < album.titel;
}

bool Album::operator<=(Album &album) {
    return this->titel <= album.titel;
}

bool Album::operator>(Album &album) {
    return this->titel > album.titel;
}

bool Album::operator>=(Album &album) {
    return this->titel >= album.titel;
}