There are tons of articles you can read from by simply googling "national socialism" and "bernie sanders." Now, yes, many of those articles are written by right leaning sites. However, there are plenty of nopartisan sites that write about this.
Throw away the labels. Read the actual definition of what is NAZI, what were their values, what were their philosopies and ideaologies. Then look at what Bernie Sanders preaches on his campaign, what he rallies for, the evidence speaks for itself.
"If anything, today's Democratic Party is certainly the party of Big Government, big spending, and authoritarianism. Senator Bernie Sanders, the "Independent" from Vermont who currently leads at least some of the Democratic presidential polling, is the embodiment of the Nazi brand of ideology."
(http://www.naturalnews.com/051787_national_socialism_Bernie_Sanders_Nazi_philosophy.html)