dG differential ghost adds a new differential equation y'=a(x)*y+b(x)
to [{x'=f(x) & Q}]P
which, when cleverly chosen,
simplifies the analysis of the resulting system after rephrasing P
in the resulting [{x'=f(x), y'=a(x)*y+b(x) & Q}]P
.
This technique is very effective to accumulate facts about the historical evolution of the ODE.
Learning resources