apt-get install gcc-4.1 出错

[linux-lion]

本机gcc4.5 由于要安装crosstool，要降gcc，实验多次失败

提示信息
Building dependency tree
Reading state information... Done
Package gcc-4.1 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'gcc-4.1' has no installation candidate

[YeLee]

坑爹的教程，连个系统版本也不说，4.1那都是多少个版本之前的事情了，难道这包还能找到？