ltsgraph: 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/ltsgraph - from package: mcrl2

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

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