I think you should read the Ebook called "Penis size does matter!" by henri dufresne.
In this ebook, they present all the existing public studies related to penis size importance. They also give weblinks for each of them. In general, theyare linked to pubmed.gov, the US national library of medecine. They also interviewed 60 women. Nevertheless, they say the human feedback is not a good information source as it is a subjective opinion.