diff --git a/src/JuliaFEM.jl b/src/JuliaFEM.jl
index b1ce349..0dcc2aa 100644
--- a/src/JuliaFEM.jl
+++ b/src/JuliaFEM.jl
@@ -6,6 +6,11 @@ This is JuliaFEM -- Finite Element Package
 """
 module JuliaFEM
 
+""" JuliaFEM Core module. """
+module Core
+include("core.jl")
+end
+
 module API
 include("api.jl")
 
@@ -27,94 +32,6 @@ module Test
 include("test.jl")
 end
 
-module Core
-
-import Base: +, -, /, *, push!, convert, getindex, setindex!, length, similar, call, vec, endof
-
-"""
-A very simple debugging macro. It prints debug message if environment variable
-JULIAFEM_DEBUG is found.
-
-Usage: instead of starting session `julia file.jl` do `JULIAFEM_DEBUG=1 julia file.jl`.
-Or set `export JULIAFEM_DEBUG=1` for your `.bashrc`.
-"""
-macro debug(msg)
-    if !haskey(ENV, "JULIAFEM_DEBUG")
-        return
-    end
-    return :( println("DEBUG: ", $msg) )
-end
-
-function set_debug_on!()
-    ENV["JULIAFEM_DEBUG"] = 1;
-end
-
-function set_debug_off!()
-    pop!(ENV, "JULIAFEM_DEBUG");
-end
-
-export @debug, set_debug_on!, set_debug_off!
-
-using ForwardDiff
-autodiffcache = ForwardDiffCache()
-# export derivative, jacobian, hessian
-
-""" Simple linspace extension to arrays.
-
-Examples
---------
->>> linspace([0.0], [1.0], 3)
-3-element Array{Array{Float64,1},1}:
- [0.0]
- [0.5]
- [1.0]
-
-"""
-function Base.linspace{T<:Array}(X1::T, X2::T, n)
-    [1/2*(1-ti)*X1 + 1/2*(1+ti)*X2 for ti in linspace(-1, 1, n)]
-end
-
-function Base.resize!(A::SparseMatrixCSC, m::Int64, n::Int64)
-    (n == A.n) && (m == A.m) && return
-    @assert n >= A.n
-    @assert m >= A.m
-    append!(A.colptr, A.colptr[end]*ones(Int, m-A.m))
-    A.n = n
-    A.m = m
-end
-
-
-# fields, see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/notebooks/2015-06-14-data-structures.ipynb
-include("fields.jl")
-#include("basis.jl")  # interpolation of discrete fields
-include("symbolic.jl") # a thin symbolic layer for fields
-include("types.jl")  # type definitions
-
-### ELEMENTS ###
-include("elements.jl")
-include("lagrange.jl") # Lagrange elements
-#include("hierarchical.jl") # P-elements
-#include("mortar_elements.jl") # Mortar elements
-
-### EQUATIONS ###
-include("integrate.jl")  # default integration points for elements
-include("sparse.jl")
-include("problems.jl")
-include("equations.jl")
-
-### FORMULATIION ###
-include("dirichlet.jl")
-include("heat.jl")
-include("elasticity.jl")
-
-### ASSEMBLY + SOLVE ###
-include("assembly.jl")
-include("solvers.jl")
-include("directsolver.jl") # parallel sparse direct solver for non-linear problems
-
-### MORTAR STUFF ###
-include("mortar.jl")  # mortar projection
-end
 
 module Interfaces
 include("interfaces.jl")
diff --git a/src/core.jl b/src/core.jl
new file mode 100644
index 0000000..427a304
--- /dev/null
+++ b/src/core.jl
@@ -0,0 +1,89 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md
+
+import Base: +, -, /, *, push!, convert, getindex, setindex!, length, similar, call, vec, endof
+
+"""
+A very simple debugging macro. It prints debug message if environment variable
+JULIAFEM_DEBUG is found.
+
+Usage: instead of starting session `julia file.jl` do `JULIAFEM_DEBUG=1 julia file.jl`.
+Or set `export JULIAFEM_DEBUG=1` for your `.bashrc`.
+"""
+macro debug(msg)
+    if !haskey(ENV, "JULIAFEM_DEBUG")
+        return
+    end
+    return :( println("DEBUG: ", $msg) )
+end
+
+function set_debug_on!()
+    ENV["JULIAFEM_DEBUG"] = 1;
+end
+
+function set_debug_off!()
+    pop!(ENV, "JULIAFEM_DEBUG");
+end
+
+export @debug, set_debug_on!, set_debug_off!
+
+using ForwardDiff
+autodiffcache = ForwardDiffCache()
+# export derivative, jacobian, hessian
+
+""" Simple linspace extension to arrays.
+
+Examples
+--------
+>>> linspace([0.0], [1.0], 3)
+3-element Array{Array{Float64,1},1}:
+ [0.0]
+ [0.5]
+ [1.0]
+
+"""
+function Base.linspace{T<:Array}(X1::T, X2::T, n)
+    [1/2*(1-ti)*X1 + 1/2*(1+ti)*X2 for ti in linspace(-1, 1, n)]
+end
+
+function Base.resize!(A::SparseMatrixCSC, m::Int64, n::Int64)
+    (n == A.n) && (m == A.m) && return
+    @assert n >= A.n
+    @assert m >= A.m
+    append!(A.colptr, A.colptr[end]*ones(Int, m-A.m))
+    A.n = n
+    A.m = m
+end
+
+
+# fields, see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/notebooks/2015-06-14-data-structures.ipynb
+include("fields.jl")
+#include("basis.jl")  # interpolation of discrete fields
+include("symbolic.jl") # a thin symbolic layer for fields
+include("types.jl")  # type definitions
+
+### ELEMENTS ###
+include("elements.jl")
+include("lagrange.jl") # Lagrange elements
+#include("hierarchical.jl") # P-elements
+#include("mortar_elements.jl") # Mortar elements
+
+### EQUATIONS ###
+include("integrate.jl")  # default integration points for elements
+include("sparse.jl")
+include("problems.jl")
+include("equations.jl")
+
+### FORMULATIION ###
+include("dirichlet.jl")
+include("heat.jl")
+include("elasticity.jl")
+
+### ASSEMBLY + SOLVE ###
+include("assembly.jl")
+include("solvers.jl")
+include("directsolver.jl") # parallel sparse direct solver for non-linear problems
+
+### MORTAR STUFF ###
+include("mortar.jl")  # mortar projection
+