Bibliography occurs twice in pdf output

[Wolfgang Engelmann]

I have a normal Bibliography setting in my Koma script book which is 
correctly shown as such in the pdf output.

I have additionally a
Recommended literature
in the book with a few references
which refers to Section 4 of my Appendix as
Recommended literature.

Strangely, this
Recommended literature
section

is listed in the pdf file also as
bibliography
so that I have
bibliography
listed twice

Strange! What am I doing wrong?

Wolfgang