alias num (instance 0) = "natural number".
alias symbol "eq" (instance 0) = "Coq's leibnitz's equality".
alias symbol "plus" (instance 0) = "Coq's natural plus".
alias num (instance 0) = "natural number".
alias symbol "eq" (instance 0) = "Coq's leibnitz's equality".
alias symbol "plus" (instance 0) = "Coq's natural plus".