an error occured while converting to manual page

while compiling my script tries and tells me:

  docbook-to-man PX_get_majorversion.sgml > PX_get_majorversion.3
  PX_get_majorversion.sgml:1: parser error : StartTag: invalid element
  name
  <!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [
   ^
  PX_get_majorversion.sgml:1: parser error : Extra content at the end of
  the document
  <!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [
   ^
  unable to parse PX_get_majorversion.sgml
  Document requires an element [Ln: 1, Col: 0]
  make[2]: *** [PX_get_majorversion.3] Fehler 9
  make[2]: Leaving directory `/usr/local/src/paradox/pxlib-0.5.1/doc'
  make[1]: *** [all-recursive] Fehler 1
  make[1]: Leaving directory `/usr/local/src/paradox/pxlib-0.5.1'
  make: *** [all] Fehler 2

Do you know what to do?

Andreas