diff --git a/ext/DensityRatioEstimationChainRulesCoreExt.jl b/ext/DensityRatioEstimationChainRulesCoreExt.jl
index 0ec4884..82e49ed 100644
--- a/ext/DensityRatioEstimationChainRulesCoreExt.jl
+++ b/ext/DensityRatioEstimationChainRulesCoreExt.jl
@@ -1,6 +1,7 @@
 # ------------------------------------------------------------------
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
+
 module DensityRatioEstimationChainRulesCoreExt
 
 if isdefined(Base, :get_extension)
diff --git a/ext/DensityRatioEstimationConvexExt.jl b/ext/DensityRatioEstimationConvexExt.jl
index d70f848..b416af8 100644
--- a/ext/DensityRatioEstimationConvexExt.jl
+++ b/ext/DensityRatioEstimationConvexExt.jl
@@ -1,6 +1,7 @@
 # ------------------------------------------------------------------
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
+
 module DensityRatioEstimationConvexExt
 
 if isdefined(Base, :get_extension)
diff --git a/ext/DensityRatioEstimationGPUArraysExt.jl b/ext/DensityRatioEstimationGPUArraysExt.jl
index c16705a..9f58743 100644
--- a/ext/DensityRatioEstimationGPUArraysExt.jl
+++ b/ext/DensityRatioEstimationGPUArraysExt.jl
@@ -1,6 +1,7 @@
 # ------------------------------------------------------------------
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
+
 module DensityRatioEstimationGPUArraysExt
 
 if isdefined(Base, :get_extension)
diff --git a/ext/DensityRatioEstimationJuMPExt.jl b/ext/DensityRatioEstimationJuMPExt.jl
index ee49421..44837d5 100644
--- a/ext/DensityRatioEstimationJuMPExt.jl
+++ b/ext/DensityRatioEstimationJuMPExt.jl
@@ -1,6 +1,7 @@
 # ------------------------------------------------------------------
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
+
 module DensityRatioEstimationJuMPExt
 
 if isdefined(Base, :get_extension)
diff --git a/ext/DensityRatioEstimationOptimExt.jl b/ext/DensityRatioEstimationOptimExt.jl
index 4b1b4f8..7dc088f 100644
--- a/ext/DensityRatioEstimationOptimExt.jl
+++ b/ext/DensityRatioEstimationOptimExt.jl
@@ -1,6 +1,7 @@
 # ------------------------------------------------------------------
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
+
 module DensityRatioEstimationOptimExt
 
 if isdefined(Base, :get_extension)
@@ -12,7 +13,9 @@ else
   using ..DensityRatioEstimation: KLIEP, LSIF, OptimLib
   using ..Optim
 end
+
 using LinearAlgebra
+
 include("../src/kliep/optim.jl")
 include("../src/lsif/optim.jl")
 
diff --git a/src/DensityRatioEstimation.jl b/src/DensityRatioEstimation.jl
index f933757..c85e275 100644
--- a/src/DensityRatioEstimation.jl
+++ b/src/DensityRatioEstimation.jl
@@ -32,27 +32,25 @@ include("lcv.jl")
 # pure Julia implementations
 include("kmm/julia.jl")
 
+# implementations that require extra dependencies
 if !isdefined(Base, :get_extension)
   using Requires
 end
-# implementations that require extra dependencies
 @static if !isdefined(Base, :get_extension)
   function __init__()
-
-    #Solvers
-
-    #JuMP: KMM, LSIF
+    # JuMP: KMM, LSIF
     @require JuMP = "4076af6c-e467-56ae-b986-b466b2749572" begin
       @require Ipopt = "b6b21f68-93f8-5de0-b562-5493be1d77c9" begin
         include("../ext/DensityRatioEstimationJuMPExt.jl")
       end
     end
-    #Optim: KLIEP, LSIF
+
+    # Optim: KLIEP, LSIF
     @require Optim = "429524aa-4258-5aef-a3af-852621145aeb" begin
       include("../ext/DensityRatioEstimationOptimExt.jl")
     end
 
-    #Convex: KLIEP
+    # Convex: KLIEP
     @require Convex = "f65535da-76fb-5f13-bab9-19810c17039a" begin
       @require ECOS = "e2685f51-7e38-5353-a97d-a921fd2c8199" begin
         include("../ext/DensityRatioEstimationConvexExt.jl")
@@ -63,7 +61,6 @@ end
     @require ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4" begin
       include("../ext/DensityRatioEstimationChainRulesCoreExt.jl")
     end
-
     @require GPUArrays = "0c68f7d7-f131-5f86-a1c3-88cf8149b2d7" begin
       include("../ext/DensityRatioEstimationGPUArraysExt.jl")
     end
diff --git a/src/kliep/convex.jl b/src/kliep/convex.jl
index d6f3bbf..9f6641f 100644
--- a/src/kliep/convex.jl
+++ b/src/kliep/convex.jl
@@ -2,7 +2,7 @@
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
 
-#This file is part of the module DensityRatioEstimationConvexExt.
+# This file is part of the module DensityRatioEstimationConvexExt.
 
 function DensityRatioEstimation._kliep_coeffs(K_nu, K_de, dre::KLIEP, optlib::Type{ConvexLib})
   # retrieve parameters
diff --git a/src/kliep/optim.jl b/src/kliep/optim.jl
index 025fe63..8074ea8 100644
--- a/src/kliep/optim.jl
+++ b/src/kliep/optim.jl
@@ -2,7 +2,7 @@
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
 
-#This file is part of the module DensityRatioEstimationOptimExt.
+# This file is part of the module DensityRatioEstimationOptimExt.
 
 function DensityRatioEstimation._kliep_coeffs(K_nu, K_de, dre::KLIEP, optlib::Type{OptimLib})
   # retrieve parameters
diff --git a/src/kmm/jump.jl b/src/kmm/jump.jl
index 13eb481..2a3dfa6 100644
--- a/src/kmm/jump.jl
+++ b/src/kmm/jump.jl
@@ -2,7 +2,7 @@
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
 
-#This file is part of the module DensityRatioEstimationJuMPExt.
+# This file is part of the module DensityRatioEstimationJuMPExt.
 
 function _kmm_jump_model(K, κ, dre::AbstractKMM, optlib::Type{JuMPLib})
   # number of denominator samples
diff --git a/src/lsif/jump.jl b/src/lsif/jump.jl
index 3c4169e..bdb4045 100644
--- a/src/lsif/jump.jl
+++ b/src/lsif/jump.jl
@@ -2,7 +2,7 @@
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
 
-#This file is part of the module DensityRatioEstimationJuMPExt.
+# This file is part of the module DensityRatioEstimationJuMPExt.
 
 function DensityRatioEstimation._lsif_coeffs(H, h, dre::LSIF, optlib::Type{JuMPLib})
   # retrieve parameters
diff --git a/src/lsif/optim.jl b/src/lsif/optim.jl
index 9c7f27d..dc90fc6 100644
--- a/src/lsif/optim.jl
+++ b/src/lsif/optim.jl
@@ -2,7 +2,7 @@
 # Licensed under the MIT License. See LICENSE in the project root.
 # ------------------------------------------------------------------
 
-#This file is part of the module DensityRatioEstimationOptimExt.
+# This file is part of the module DensityRatioEstimationOptimExt.
 
 function DensityRatioEstimation._lsif_coeffs(H, h, dre::LSIF, optlib::Type{OptimLib})
   # retrieve parameters