Question: Infinitesimal optional and prolongation of PDE

my question is a little bit long but is not complicated, i want find thus  unkown but  realy i am don't know how apply on it by maple, i have two best paper which explain very well i just want to find thus dimensional Lie algebra which is be invariant or not satisfy condition or not which i have to used or which i have not to use it also the importan part how find them in paper 1 first , for equation fisher 
How find eq(29) which is i think is two -dimensional Lie algebra of equation, also the best part is reduction which by apply this we can change PDE to ode but i don't know how apply eq(31) or even find it yet  is related to eq(27-28)  and by replacing equation eq(34) we can get our ode i am just loking for the ode, for the eq(76) and eq(85) have same procedures,  i will mention the paper link too 

Lie.mw

paper-1

paper-2