I read the book of "quantum field theory in nutshell" by A. Zee. There is a "baby problem" in Page 44. I can't understand how to get the diagrams of Figure 1.7.1 from the calculation of -(\lambda/4!)(d/dJ)^4 differentiating [1/4!(2m^2)^4]J^8. How to associate this term to the three diagrams? Can anybody give a detailed explanation? very appreciation! maybe I am a very weak baby.