xml2ris: 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 CentOS possible default full paths are:

/usr/bin/xml2ris - from package: bibutils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/xml2ris - from package: bibutils

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

Error in other languages:
xml2ris: bevel nie gevind nie
xml2ris: comandă negăsită
xml2ris: comando não encontrado
xml2ris: commande introuvable
xml2ris: command not found
xml2ris: käsku ei ole
xml2ris: không tìm thấy lệnh
xml2ris: komanda nerasta
xml2ris: Kommando nicht gefunden.
xml2ris: kommandot finns inte
xml2ris: komut yok
xml2ris: nie znaleziono polecenia
xml2ris: níor aimsíodh an t-ordú
xml2ris: no se encontró la orden
xml2ris: no s'ha trobat l'ordre
xml2ris: opdracht niet gevonden
xml2ris: parancs nem található
xml2ris: perintah tidak ditemukan
xml2ris: príkaz nenájdený
xml2ris: příkaz nenalezen
xml2ris: команда не найдена
xml2ris: командата не е открита
xml2ris: 命令找不到
xml2ris: コマンドが見つかりません