DOCBOOK: cannot generate system identifier for public text"-//OASIS//DTD DocBook V4.1//EN"

[Kohler Benjamin <Benjamin dot Kohler at vpbank dot com>]

Hello,
First sorry if this question is OT. I am absolute SGML a beginner.
When i would make my sglm document to html with sgml2txt, comes this
errors:
sgml2txt systemdoku_server.txt
Processing file systemdoku_server.txt
/usr/bin/nsgmls:<OSFD>0:1:54:W: cannot generate system identifier for public
text "-//OASIS//DTD DocBook V4.1//EN"
/usr/bin/nsgmls:<OSFD>0:1:54:E: reference to entity "BOOK" for which no
system identifier could be generated
/usr/bin/nsgmls:<OSFD>0:1:0: entity was defined here
/usr/bin/nsgmls:<OSFD>0:1:54:E: DTD did not contain element declaration for
document type name
/usr/bin/nsgmls:<OSFD>0:2:5:E: element "BOOK" undefined
/usr/bin/nsgmls:<OSFD>0:3:9:E: element "BOOKINFO" undefined
/usr/bin/nsgmls:<OSFD>0:4:6:E: element "TITLE" undefined
/usr/bin/nsgmls:<OSFD>0:5:12:E: element "AUTHORGROUP" undefined
/usr/bin/nsgmls:<OSFD>0:6:7:E: element "AUTHOR" undefined
/usr/bin/nsgmls:<OSFD>0:7:10:E: element "FIRSTNAME" undefined
/usr/bin/nsgmls:<OSFD>0:8:8:E: element "SURNAME" undefined
/usr/bin/nsgmls:<OSFD>0:9:12:E: element "AFFILIATION" undefined
/usr/bin/nsgmls:<OSFD>0:10:11:E: element "SHORTAFFIL" undefined
/usr/bin/nsgmls:<OSFD>0:14:8:E: element "PUBDATE" undefined
/usr/bin/nsgmls:<OSFD>0:15:8:E: element "EDITION" undefined
/usr/bin/nsgmls:<OSFD>0:16:10:E: element "COPYRIGHT" undefined
/usr/bin/nsgmls:<OSFD>0:17:5:E: element "YEAR" undefined
/usr/bin/nsgmls:<OSFD>0:18:7:E: element "HOLDER" undefined
/usr/bin/nsgmls:<OSFD>0:21:8:E: element "CHAPTER" undefined
/usr/bin/nsgmls:<OSFD>0:22:6:E: element "TITLE" undefined
/usr/bin/nsgmls:<OSFD>0:141:21:E: character "," not allowed in attribute
specification list
/usr/bin/nsgmls:<OSFD>0:141:21:E: element "UP" undefined
/usr/bin/nsgmls:<OSFD>0:143:22:E: character "," not allowed in attribute
specification list
/usr/bin/nsgmls:<OSFD>0:143:22:E: element "UP" undefined
/usr/bin/nsgmls:<OSFD>0:1221:2:E: end tag for "UP" omitted, but its
declaration does not permit this
/usr/bin/nsgmls:<OSFD>0:143:19: start tag was here
/usr/bin/nsgmls:<OSFD>0:1221:2:E: end tag for "UP" omitted, but its
declaration does not permit this
/usr/bin/nsgmls:<OSFD>0:141:18: start tag was here
/usr/bin/nsgmls:<OSFD>0:1221:2:E: end tag for "CHAPTER" omitted, but its
declaration does not permit this
/usr/bin/nsgmls:<OSFD>0:21:0: start tag was here
/usr/bin/nsgmls:<OSFD>0:1221:2:E: end tag for "BOOK" omitted, but its
declaration does not permit this
/usr/bin/nsgmls:<OSFD>0:2:0: start tag was here
/usr/bin/sgmlsasp: can't open `/usr/lib/sgml-tools/dist/book/groff/mapping':
No such file or directory 
[kob@uligugux001 kob]$

I have installed the folling packages (rpm) on a Redhat 7.2 System:
[kob@uligugux001 kob]$ uname -a 
Linux uligugux001 2.4.7-10 #1 Thu Sep 6 17:27:27 EDT 2001 i686 unknown
[kob@uligugux001 kob]$ rpm -qa ¦grep sgml
[kob@uligugux001 kob]$ rpm -qa |grep sgml
docbook-dtd31-sgml-1.0-10
docbook-dtd30-sgml-1.0-10
docbook-dtd40-sgml-1.0-11
sgml-tools-1.0.9-12
sgml-common-0.5-7
docbook-dtd41-sgml-1.0-10
[kob@uligugux001 kob]$

And here are the configs
[kob@uligugux001 sgml]$ cat sgml.conf 
# /etc/sgml/sgml.conf conformant with LSB
SGML_BASE_DIR=/usr/share/sgml/
SGML_CATALOGS_DIR=/etc/sgml
[kob@uligugux001 sgml]$ cat sgml-docbook-4.1.cat 
CATALOG /usr/share/sgml/sgml-iso-entities-8879.1986/catalog
CATALOG /usr/share/sgml/docbook/sgml-dtd-4.1/catalog
CATALOG /usr/share/sgml/openjade-1.3/catalog
CATALOG /usr/share/sgml/docbook/dsssl-stylesheets-1.64/catalog
[kob@uligugux001 sgml]$  

Any hints?

cu
kob