void setUsed(bool u) const { used_ = u; }
///
bool used() const { return used_; }
///
friend std::istream & operator>>(std::istream & os, Author & a);
void setUsed(bool u) const { used_ = u; }
///
bool used() const { return used_; }
///
friend std::istream & operator>>(std::istream & os, Author & a);