diff --git a/src/LabProcesses.jl b/src/LabProcesses.jl
index 6cd40f1c52c83d2144972eeed8d58057beb56c6c..df0f70dacd65925d9821dd1abf3db85c302b5eb3 100644
--- a/src/LabProcesses.jl
+++ b/src/LabProcesses.jl
@@ -3,6 +3,7 @@ module LabProcesses
 using ControlSystems
 
 include("interface.jl")
+include("interface_documentation.jl")
 include("interface_implementations/ballandbeam.jl")
 
 include("utilities.jl")
diff --git a/src/interface_documentation.jl b/src/interface_documentation.jl
index fa3f18ff4d3f5a8293a74e109d23a4020199f135..59e6de51540fc76e796c1b403524eac6ce167317 100644
--- a/src/interface_documentation.jl
+++ b/src/interface_documentation.jl
@@ -7,13 +7,13 @@ Base abstract type for all lab processes. This should not be inherited from dire
 AbstractProcess
 
 """
-    PhysicalProcess
+    PhysicalProcess <: AbstractProcess
 Pysical processes should inherit from this abstract type.
 """
 PhysicalProcess
 
 """
-    SimulatedProcess
+    SimulatedProcess <: AbstractProcess
 Simulated processes should inherit from this abstract type.
 """
 SimulatedProcess
@@ -38,7 +38,7 @@ tuples,  `length(range) = num_outputs(P), eltype(range) = Tuple(Real, Real)`
 outputrange
 
 """
-    inputrange(P::AbstractProcess)
+    range = inputrange(P::AbstractProcess)
 Return the range of inputs (control signals) of the process. `range` is a vector of
 tuples,  `length(range) = num_inputs(P), eltype(range) = Tuple(Real, Real)`
 """