/// <summary>Initializes a new instance of the <see cref="AtomEntry"/> class with an ID, title, and date and time when the entry was last updated.</summary>
 /// <param name="id">An <see cref="AtomId"/> representing the ID of the entry.</param>
 /// <param name="title">An <see cref="AtomTitle"/> representing the title of the entry.</param>
 /// <param name="updated">An <see cref="AtomUpdated"/> representing the date and time when the entry was last updated.</param>
 /// <exception cref="ArgumentNullException"><paramref name="id"/>, <paramref name="title"/>, or <paramref name="updated"/> is null.</exception>
 public AtomEntry(AtomId id, AtomTitle title, AtomUpdated updated)
   : base(id, title, updated)
 {
   if(id == null) throw new ArgumentNullException("id");
   if(title == null) throw new ArgumentNullException("title");
   if(updated == null) throw new ArgumentNullException("updated");
 }
 /// <summary>Initializes a new instance of the <see cref="AtomFeed"/> class with an ID, title, and date and time when the feed was last updated.</summary>
 /// <param name="id">An <see cref="AtomId"/> representing the ID of the feed.</param>
 /// <param name="title">An <see cref="AtomTitle"/> representing the title of the feed.</param>
 /// <param name="updated">An <see cref="AtomUpdated"/> representing the date and time when the feed was last updated.</param>
 /// <exception cref="ArgumentNullException"><paramref name="id"/>, <paramref name="title"/>, or <paramref name="updated"/> is null.</exception>
 public AtomFeed(AtomId id, AtomTitle title, AtomUpdated updated)
   : base(id, title, updated)
 {
   if(id == null) throw new ArgumentNullException("id");
   if(title == null) throw new ArgumentNullException("title");
   if(updated == null) throw new ArgumentNullException("updated");
   base.Generator = new AtomGenerator();
 }
 /// <summary>Initializes a new instance of the <see cref="AtomSource"/> class with an ID, title, and date and time when the entry was last updated.</summary>
 /// <param name="id">An <see cref="AtomId"/> representing the ID of the source.</param>
 /// <param name="title">An <see cref="AtomTitle"/> representing the title of the source.</param>
 /// <param name="updated">An <see cref="AtomUpdated"/> representing the date and time when the source was last updated.</param>
 /// <exception cref="ArgumentNullException"><paramref name="id"/>, <paramref name="title"/>, or <paramref name="updated"/> is null.</exception>
 public AtomSource(AtomId id, AtomTitle title, AtomUpdated updated) : base(id, title, updated) { }