BerenstEin, it always was. Then my daughter got a handful of those books after she was born, and damn, they changed it? BerenstAin, wtf?!?! So I asked friends, parents, etc., all agreed it was spelled like Einstein. But according to the family it was always Berenstain, dating back to immigration. A quick Google starts down the rabbit hole pretty damn fast:
http://woodbetweenworlds.blogspot.com/2012/08/the-berenstein-bears-we-are-living-in.html
http://cjaymarch.wikia.com/wiki/The_Berenstain_Bears_are_a_Lie
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http://woodbetweenworlds.blogspot.com/2012/08/the-berenstein-bears-we-are-living-in.html
http://cjaymarch.wikia.com/wiki/The_Berenstain_Bears_are_a_Lie
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