 As soon as he was well enough to write again, he began work on "Time Enough for Love" (1973), which introduced many of the themes found in his later fiction.In the mid-1970s, Heinlein wrote two articles for the "Britannica Compton Yearbook".He and Ginny crisscrossed the country helping to reorganize blood donation in the United States in an effort to assist the system which had saved his life.