[Zope] _setOb vs. _setObject in BTreeFolder

[Thomas Guettler]

What is the difference between _setObject and _setOb in a BTreeFolder?

I discovered that if I use _setObject the BTreeFolder is not used, but 
when I use _setOb
it used, but the documents don't appear in mybtreefolder/manage_main.

BTreeFolder seems to have to storages: the inherited ones from Folder 
and the BTree storage.
This is confusing. I think it would be better if BTreeFolder would 
delegate all methods to _tree,
or rise an exception if you try to write the Folder storage.

BTreeFolder doesn't display the addProdukt drop-down box properly, too.

I use BTreeFolder version 0.2 from February 2001.

Are others having this problems, too?