Document type definition. A document type definition (DTD) is a set of markup declarations that define a document type for an SGML-family markup language (SGML, XML, HTML). A Document Type Definition (DTD) defines the legal building blocks of an XML document. It defines the document structure with a list of legal elements and attributes. A DTD can be declared inline inside an XML document, or as an external reference.
American hornbeam. The American hornbeam is a native forest understory tree in the Chicago area, making it useful for shady landscapes and naturalized or woodland gardens.New leaves emerge reddish-purple, changing to dark green, then turn yellow to orange-red in the fall, offering a kaleidoscope of color throughout the year.merican hornbeam. The American hornbeam is a native forest understory tree in the Chicago area, making it useful for shady landscapes and naturalized or woodland gardens.
Causes. The exact cause of a cutaneous horn is still not known but what is known is that many of them appear on skin that has been over exposed to the sun. Some believe that being exposed to radiation can trigger a cutaneous horn which is evidenced by a higher rate of cutaneous horns on the hands and feet.