matitaclean: 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/matitaclean - from package: matita

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

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