President Reagan, in his closing remarks on Central America, refers to the book "Power Through Subversion," by Laurence W. Beilenson. (Public Affairs, 1972). The official note-taker spelled Mr. Beilenson's name incorrectly. This error was caught by David Hoffman, of the Washington Post. Mr. Hoffman's new book, "The Dead Hand: The Untold Story of the Cold War Arms Race And Its Dangerous Legacy," is now out and available at Amazon.com.