It is important to remember when using mapReduce() that the return value of the reduce() function needs to be the same shape as the one that you expect to get in the 'values' element of reduce() function -- and that, in turn, needs to be the same shape as what is emitted by the emit() function.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.