sgml2x: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/sgml2x - from package: sgml2x

You may install the required package with command apt-get install {package}

Error in other languages:
sgml2x: bevel nie gevind nie
sgml2x: comandă negăsită
sgml2x: comando não encontrado
sgml2x: commande introuvable
sgml2x: command not found
sgml2x: käsku ei ole
sgml2x: không tìm thấy lệnh
sgml2x: komanda nerasta
sgml2x: Kommando nicht gefunden.
sgml2x: kommandot finns inte
sgml2x: komut yok
sgml2x: nie znaleziono polecenia
sgml2x: níor aimsíodh an t-ordú
sgml2x: no se encontró la orden
sgml2x: no s'ha trobat l'ordre
sgml2x: opdracht niet gevonden
sgml2x: parancs nem található
sgml2x: perintah tidak ditemukan
sgml2x: príkaz nenájdený
sgml2x: příkaz nenalezen
sgml2x: команда не найдена
sgml2x: командата не е открита
sgml2x: 命令找不到
sgml2x: コマンドが見つかりません