Hi Geni,
@Isaac Samuel Avigdor is my fourth great grandfather. Until recently, there were no ancestors for Isaac Samuel Avigdor. I presume these were added by @Mordechai Naftalis on 26th January 2015. I am curious to know if these were taken directly from http://genebour.fr/ curated by Jean-Paul BOURLAC, am I correct?
I have been in contact with a history professor in Nice, and one of his Masters students by in 2006-2007 did a study on the Avigdor Family tracing it back to Leon Avigdor in 1608, who I believe established the Avigdor Family settlement in Nice. Both this paper (which he kindly provided), along with the paper by Hildesheim (link in the 'Overview' section), states that his father is <Moise Avigdor>, and not <Samuel Avigdor>. Perhaps one is his middle name? Abraham Avigdor appears to be his uncle on all accounts though.
There appears to discrepancies in all three family trees, and it shows just how difficult genalogical studies can be!!!