The answer to the crossword puzzle is MAO and TAO, which refer to Mao Zedong and the Tao Te Ching, respectively. Mao Zedong was a Chinese communist revolutionary and the founding father of the People's Republic of China. He is best known for his book, the Little Red Book, which was a collection of quotations from his speeches and writings. The Tao Te Ching is an ancient Chinese text written by Lao Tzu, which is considered to be the foundation of Taoism. Both Mao Zedong and Lao Tzu are the authors of the Little Red Book.