Boston, New York Ginn and Co. [http://books.google.com/books?vid=ISBN0766146243&id=VR3RlmT521QC&printsec=frontcover view online here* Jackson E Christine (2013).
Boston, New York Ginn and Co. [http://books.google.com/books?vid=ISBN0766146243&id=VR3RlmT521QC&printsec=frontcover Просмотр он-лайн* Punke, Michael (2007).