diff --git a/.travis.yml b/.travis.yml
index c189118..34dc7ce 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,12 +6,18 @@ os:
 julia:
   - release
   - nightly
+matrix:
+  fast_finish: true
+  allow_failures:
+    julia: nightly
+
 notifications:
   email: false
 # uncomment the following lines to override the default test script
-#script:
-#  - if [[ -a .git/shallow ]]; then git fetch --unshallow; fi
-#  - julia -e 'Pkg.clone(pwd()); Pkg.build("Groups"); Pkg.test("Groups"; coverage=true)'
+script:
+  - if [[ -a .git/shallow ]]; then git fetch --unshallow; fi
+  - julia -e 'Pkg.clone("https://github.com/scheinerman/Permutations.jl.git")'
+  - julia -e 'Pkg.clone(pwd()); Pkg.build("Groups"); Pkg.test("Groups"; coverage=true)'
 after_success:
   # push coverage results to Coveralls
   - julia -e 'cd(Pkg.dir("Groups")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())'
diff --git a/REQUIRE b/REQUIRE
index 9a19caf..fee6ae7 100644
--- a/REQUIRE
+++ b/REQUIRE
@@ -1,2 +1,3 @@
 julia 0.5
 Permutations
+Combinatorics
diff --git a/src/Groups.jl b/src/Groups.jl
index 3b4a7b3..910cd4f 100644
--- a/src/Groups.jl
+++ b/src/Groups.jl
@@ -1,7 +1,8 @@
 module Groups
 
-import Base: length, ==, hash, show
+import Base: length, ==, hash, show, convert
 import Base: one, inv, reduce, *, ^
+import Base: findfirst, findnext
 
 export GSymbol, GWord
 
@@ -41,6 +42,7 @@ type GWord{T<:GSymbol} <: Word
 end
 
 GWord{T<:GSymbol}(s::T) = GWord{T}([s])
+convert{T<:GSymbol, W<:Word}(::Type{W}, s::T) = GWord{T}(s)
 
 IDWord{T<:GSymbol}(::Type{T}) = GWord(one(T))
 IDWord{T<:GSymbol}(W::GWord{T}) = IDWord(T)
@@ -94,7 +96,10 @@ end
 
 freegroup_reduce(W::GWord) = freegroup_reduce!(deepcopy(W))
 
-hash{T}(W::GWord{T}) = (W.modified && freegroup_reduce!(W); W.savedhash)
+function hash{T}(W::GWord{T}, h::UInt)
+    W.modified && freegroup_reduce!(W)
+    return W.savedhash + h
+end
 
 function (==){T}(W::GWord{T}, Z::GWord{T})
      W.modified && freegroup_reduce!(W) # reduce clears the flag and recalculate the hash
@@ -172,6 +177,72 @@ end
 (^)(x::GWord, n::Integer) = power_by_squaring(x,n)
 (^){T<:GSymbol}(x::T, n::Integer) = GWord(x)^n
 
+is_subsymbol(s::GSymbol, t::GSymbol) =
+    s.gen == t.gen && (0 ≤ s.pow ≤ t.pow || 0 ≥ s.pow ≥ t.pow)
+
+function findfirst(W::GWord, Z::GWord)
+    n = length(Z.symbols)
+
+    @assert n > 1
+    for (idx,a) in enumerate(W.symbols)
+        if idx + n - 1 > length(W.symbols)
+            break
+        end
+        first = is_subsymbol(Z.symbols[1],a)
+        if first
+            middle = W.symbols[idx+1:idx+n-2] == Z.symbols[2:end-1]
+            last = is_subsymbol(Z.symbols[end], W.symbols[idx+n-1])
+            if middle && last
+                return idx
+            end
+        end
+    end
+    return 0
+end
+
+function findnext(W::GWord, Z::GWord, i::Integer)
+    t = findfirst(GWord{eltype(W.symbols)}(W.symbols[i:end]), Z)
+    if t > 0
+        return t+i-1
+    else
+        return 0
+    end
+end
+
+function replace!(W::GWord, index, toreplace::GWord, replacement::GWord; asserts=true)
+    n = length(toreplace.symbols)
+    if asserts
+        @assert is_subsymbol(toreplace.symbols[1], W.symbols[index])
+        @assert W.symbols[index+1:index+n-2] == toreplace.symbols[2:end-1]
+        @assert is_subsymbol(toreplace.symbols[end], W.symbols[index+n-1])
+    end
+
+    first = W.symbols[index]*inv(toreplace.symbols[1])
+    last = W.symbols[index+n-1]*inv(toreplace.symbols[end])
+    replacement = first*replacement*last
+    splice!(W.symbols, index:index+n-1, replacement.symbols)
+    Groups.freegroup_reduce!(W)
+    return W
+end
+
+function replace(W::GWord, index, toreplace::GWord, replacement::GWord)
+    replace!(deepcopy(W), index, toreplace, replacement)
+end
+
+function replace_all!{T}(W::GWord{T}, subst_dict::Dict{GWord{T}, GWord{T}})
+    for toreplace in reverse!(sort!(collect(keys(subst_dict)),by=length))
+        replacement = subst_dict[toreplace]
+        i = findfirst(W, toreplace)
+        while i ≠ 0
+            replace!(W,i,toreplace, replacement)
+            i = findnext(W, toreplace, i)
+        end
+    end
+    return W
+end
+
+replace_all(W::GWord, subst_dict::Dict{GWord, GWord}) = replace_all!(deepcopy(W), subst_dict)
+
 include("free_groups.jl")
 include("automorphism_groups.jl")
 
diff --git a/src/automorphism_groups.jl b/src/automorphism_groups.jl
index 51d2a48..25ee5a1 100644
--- a/src/automorphism_groups.jl
+++ b/src/automorphism_groups.jl
@@ -7,19 +7,31 @@ immutable AutSymbol <: GSymbol
     gen::String
     pow::Int
     ex::Expr
+    fmap::Function
+    imap::Function
+end
+
+function (f::AutSymbol){T}(v::Vector{GWord{T}})
+    if f.pow > 0
+        map = f.fmap
+    else
+        map = f.imap
+    end
+    for i in 1:abs(f.pow)
+         v::Vector{GWord{T}} = map(v)
+    end
+    return v
 end
 
 (==)(s::AutSymbol, t::AutSymbol) = s.gen == t.gen && s.pow == t.pow
 hash(s::AutSymbol, h::UInt) = hash(s.gen, hash(s.pow, hash(:AutSymbol, h)))
 
-IdSymbol(::Type{AutSymbol}) = AutSymbol("(id)", 0, :(IdAutomorphism(N)))
+IdSymbol(::Type{AutSymbol}) = AutSymbol("(id)", 0, :(Id(N)), v -> Vector{GWord}(v), v -> Vector{GWord}(v))
 
 function change_pow(s::AutSymbol, n::Int)
-
     if n == 0
         return one(s)
     end
-
     symbol = s.ex.args[1]
     if symbol == :ɛ
         return flip_AutSymbol(s.ex.args[2], pow=n)
@@ -29,29 +41,58 @@ function change_pow(s::AutSymbol, n::Int)
         return rmul_AutSymbol(s.ex.args[2], s.ex.args[3], pow=n)
     elseif symbol == :λ
         return lmul_AutSymbol(s.ex.args[2], s.ex.args[3], pow=n)
-    elseif symbol == :IdAutomorphism
+    elseif symbol == :Id
         return s
     else
         warn("Changing an unknown type of symbol! $s")
-        return AutSymbol(s.gen, n, s.ex)
+        return AutSymbol(s.gen, n, s.ex, s.fmap, s.imap)
     end
 end
 
 inv(f::AutSymbol) = change_pow(f, -f.pow)
 
+function ϱ(i,j)
+    # @assert i ≠ j
+    return v -> [(k!=i ? GWord(v[k]) : v[i]*v[j]) for k in eachindex(v)]
+end
+
+function ϱ_inv(i,j)
+    # @assert i ≠ j
+    return v -> [(k!=i ? GWord(v[k]) : v[i]*v[j]^-1) for k in eachindex(v)]
+end
+
+
+function λ(i,j)
+    # @assert i ≠ j
+    return v -> ([(k!=i ? GWord(v[k]) : v[j]*v[i]) for k in eachindex(v)])
+end
+
+function λ_inv(i,j)
+    # @assert i ≠ j
+    return v -> ([(k!=i ? GWord(v[k]) : v[j]^-1*v[i]) for k in eachindex(v)])
+end
+
+
+ɛ(i) = v -> [(k!=i ? GWord(v[k]) : v[k]^-1) for k in eachindex(v)]
+
+function σ(perm)
+    # @assert sort(perm) == collect(1:length(perm))
+    return v -> [GWord(v[perm[k]]) for k in eachindex(v)]
+end
+
 function rmul_AutSymbol(i,j; pow::Int=1)
     gen = string('ϱ',Char(8320+i), Char(8320+j)...)
-    return AutSymbol(gen, pow, :(ϱ($i,$j)))
+    return AutSymbol(gen, pow, :(ϱ($i,$j)), ϱ(i,j), ϱ_inv(i,j))
 end
 
 function lmul_AutSymbol(i,j; pow::Int=1)
     gen = string('λ',Char(8320+i), Char(8320+j)...)
-    return AutSymbol(gen, pow, :(λ($i,$j)))
+    return AutSymbol(gen, pow, :(λ($i,$j)), λ(i,j), λ_inv(i,j))
 end
 
 function flip_AutSymbol(j; pow::Int=1)
     gen = string('ɛ', Char(8320 + j))
-    return AutSymbol(gen, (2+ pow%2)%2, :(ɛ($j)))
+    return AutSymbol(gen, (2+ pow%2)%2, :(ɛ($j)), ɛ(j), ɛ(j))
 end
 
 function symmetric_AutSymbol(perm::Vector{Int}; pow::Int=1)
@@ -59,11 +100,12 @@ function symmetric_AutSymbol(perm::Vector{Int}; pow::Int=1)
     ord = order(perm)
     pow = pow % ord
     perm = perm^pow
-    if array(perm) == collect(1:length(perm))
+    p = array(perm)
+    if p == collect(1:length(p))
         return one(AutSymbol)
     else
-        gen = string('σ', [Char(8320 + i) for i in array(perm)]...)
-        return AutSymbol(gen, 1, :(σ($(array(perm)))))
+        gen = string('σ', [Char(8320 + i) for i in p]...)
+        return AutSymbol(gen, 1, :(σ($p)), σ(p), σ(array(inv(perm))))
     end
 end
 
@@ -77,6 +119,13 @@ end
 
 typealias AutWord GWord{AutSymbol}
 
+function (F::AutWord)(v)
+    for f in F.symbols
+        v = f(v)
+    end
+    return v
+end
+
 convert(::Type{AutWord}, s::AutSymbol) = GWord(s)
 
 function simplify_perms!(W::AutWord)
@@ -100,5 +149,6 @@ function simplify_perms!(W::AutWord)
             end
         end
     end
+    deleteat!(W.symbols, find(x -> x.pow == 0, W.symbols))
     return reduced
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 7ed2238..d32f6d2 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -40,9 +40,15 @@ end
         @test isa(Groups.GWord(s), Groups.GWord)
         @test isa(Groups.GWord(s), FGWord)
         @test isa(FGWord(s), Groups.GWord)
+        @test isa(convert(FGWord, s), GWord)
+        @test isa(convert(FGWord, s), FGWord)
+        @test isa(Vector{FGWord}([s,t]), Vector{FGWord})
+        @test Vector{GWord{FGSymbol}}([s,t]) == Vector{FGWord}([s,t])
         @test isa(s*s, FGWord)
         @test s*s == s^2
         @test t*s ≠ s*t
+        @test Vector{GWord}([s,t]) == [s^2*s^-1, t]
+        @test hash([t^1,s^1]) == hash([t^2*inv(t),s*inv(s)*s])
     end
     @testset "eltary functions" begin
         @test length(FGWord(s)) == 1
@@ -56,6 +62,7 @@ end
         @test isa(one(w), FGWord)
         @test inv(s*t) == t^-1*s^-1
         @test inv(w) == s*t^-1*s^-1
+
     end
 
     @testset "reductions" begin
@@ -80,11 +87,33 @@ end
         @test (t*s*t^-1)^10 == t*s^10*t^-1
         @test (t*s*t^-1)^-10 == t*s^-10*t^-1
     end
+
+    @testset "replacements" begin
+        @test Groups.is_subsymbol(s, Groups.change_pow(s,2)) == true
+        @test Groups.is_subsymbol(s, Groups.change_pow(s,-2)) == false
+        @test Groups.is_subsymbol(t, Groups.change_pow(s,-2)) == false
+        @test Groups.is_subsymbol(inv(t), Groups.change_pow(t,-2)) == true
+        c = s*t*s^-1*t^-1
+        @test findfirst(c, s^-1*t^-1) == 3
+        @test findnext(c*s^-1, s^-1*t^-1,3) == 3
+        @test findnext(c*s^-1*t^-1, s^-1*t^-1,4) == 5
+        @test findfirst(c*t, c) == 0
+        w = s*t*s^-1
+        subst = Dict{FGWord, FGWord}(w => s^1, s*t^-1 => t^4)
+        @test Groups.replace(c, 1, s*t, one(FGWord)) == s^-1*t^-1
+
+        @test Groups.replace(c, 1, w, subst[w]) == s*t^-1
+        @test Groups.replace(s*c*t^-1, 1, w, subst[w]) == s^2*t^-2
+        @test Groups.replace(t*c*t, 2, w, subst[w]) == t*s
+        @test Groups.replace_all!(s*c*s*c*s, subst) == s*t^4*s*t^4*s
+    end
+end
+
 @testset "Automorphisms" begin
     @testset "AutSymbol" begin
         @test_throws MethodError AutSymbol("a")
         @test_throws MethodError AutSymbol("a", 1)
-        f = AutSymbol("a", 1, :(a(0)))
+        f = AutSymbol("a", 1, :(a(0)), v -> v, v -> v)
         @test isa(f, GSymbol)
         @test isa(f, AutSymbol)
         @test isa(symmetric_AutSymbol([1,2,3,4]), AutSymbol)
@@ -94,7 +123,7 @@ end
     end
 
     @testset "AutWords" begin
-        f = AutSymbol("a", 1, :(a(0)))
+        f = AutSymbol("a", 1, :(a(0)), v -> v, v -> v)
         @test isa(GWord(f), GWord)
         @test isa(GWord(f), AutWord)
         @test isa(AutWord(f), AutWord)
@@ -120,4 +149,30 @@ end
         @test a*b == b*a
         @test a^3 * b^3 == one(a)
     end
+    @testset "specific Aut(𝔽₄) tests" begin
+        N = 4
+        import Combinatorics.nthperm
+        SymmetricGroup(n) = [nthperm(collect(1:n), k) for k in 1:factorial(n)]
+        indexing = [[i,j] for i in 1:N for j in 1:N if i≠j]
+
+        σs = [symmetric_AutSymbol(perm) for perm in SymmetricGroup(N)[2:end]];
+        ϱs = [rmul_AutSymbol(i,j) for (i,j) in indexing]
+        λs = [lmul_AutSymbol(i,j) for (i,j) in indexing]
+        ɛs = [flip_AutSymbol(i) for i in 1:N];
+
+        S = vcat(ϱs, λs, σs, ɛs)
+        S = vcat(S, [inv(s) for s in S])
+        @test isa(S, Vector{AutSymbol})
+        @test length(S) == 102
+        @test length(unique(S)) == 75
+        S₁ = [GWord(s) for s in unique(S)]
+        @test isa(S₁, Vector{AutWord})
+        p = prod(S₁)
+        @test length(p) == 75
+        @test Groups.simplify_perms!(p) == false
+        @test length(p) == 53
+        @test Groups.join_free_symbols!(p) == true
+
+
+    end
 end