What is an example of allusion in the novel, Wish You Were Here?

The poisonous apples are emblems of Diana’s desire to return to the safety and security of her past life. An allusion to both Snow White and the story of Adam and Eve, the poisonous apple represents the negative effects of Diana’s life in New York. At first, both the apple and her life seem safe and normal. Upon further examination, the apple harms Diana with its poison and Diana’s life holds her back from true happiness. Gabriel saves her from eating the apple and returning to the predictability and subsequent ennui of her life in New York.