Top bottom diagram.
A-->B B-->C B-->D C-->D
https://p101007003-dot-nitokucom.uc.r.appspot.com/frame/@nitoku.public/topBottom?tk=pu&us=pu
Top bottom diagram syntax
https://p101007003-dot-nitokucom.uc.r.appspot.com/frame/@nitoku.design/nitokuQuestions?tk=pu&us=pu
https://p101007003-dot-nitokucom.uc.r.appspot.com/frame/@nitoku.design/license?tk=pu&us=pu
