diff --git a/README.md b/README.md
index 4da957ae..2a00f413 100644
--- a/README.md
+++ b/README.md
@@ -152,7 +152,9 @@ plot(M; controlpoints=(markersize=2,))
 ![](docs/src/img/rational_bspline_surface_plotly.png)
 
 ### Refinement
-#### h-refinement
+#### h-refinement (knot insertion)
+Insert additional knots to knot vectors without changing the shape.
+
 ```julia
 k₊ = (KnotVector([3.1, 3.2, 3.3]), KnotVector([0.5, 0.8, 0.9])) # additional knot vectors
 M_h = refinement(M, k₊) # refinement of B-spline manifold
@@ -160,9 +162,9 @@ plot(M_h; controlpoints=(markersize=2,))
 ```
 ![](docs/src/img/rational_bspline_surface_href_plotly.png)
 
-Note that this shape and the last shape are equivalent.
+#### p-refinement (degree elevation)
+Increase the polynomial degrees of B-spline manifold without changing the shape.
 
-#### p-refinement
 ```julia
 p₊ = (Val(1), Val(2)) # additional degrees
 M_p = refinement(M, p₊) # refinement of B-spline manifold
@@ -170,8 +172,6 @@ plot(M_p; controlpoints=(markersize=2,))
 ```
 ![](docs/src/img/rational_bspline_surface_pref_plotly.png)
 
-Note that this shape and the last shape are equivalent.
-
 ### Fitting B-spline manifold
 The next example shows the fitting for [the following graph on Desmos graphing calculator](https://www.desmos.com/calculator/2hm3b1fbdf)!
 
diff --git a/docs/make.jl b/docs/make.jl
index 319c21e0..29f320ca 100644
--- a/docs/make.jl
+++ b/docs/make.jl
@@ -6,6 +6,7 @@ using InteractiveUtils
 using Plots
 using Random
 
+ENV["GKSwstype"] = "100"
 gr()
 plotly()
 Random.seed!(42)
@@ -26,7 +27,7 @@ function generate_indexmd_from_readmemd()
     text_index = replace(text_index, r"\$\$((.|\n)*?)\$\$" => s"```math\1```")
     text_index = replace(text_index, "(https://hyrodium.github.io/BasicBSpline.jl/dev/math/bsplinebasis/#Differentiability-and-knot-duplications)" => "(@ref differentiability-and-knot-duplications)")
     text_index = replace(text_index, r"https://github.com/hyrodium/BasicBSpline\.jl/assets/.*" => "![](math/differentiability.mp4)")
-    text_index = replace(text_index, "```julia\njulia>" => "```julia-repl\njulia>")
+    text_index = replace(text_index, "```julia\njulia>" => "```jldoctest\njulia>")
     text_index = replace(text_index, "```julia\n" => "```@example readme\n")
     text_index = replace(text_index, r"```\n!\[\]\(docs/src/img/(.*?)plotly\.png\)" => s"savefig(\"readme-\1plotly.html\") # hide\nnothing # hide\n```\n```@raw html\n<object type=\"text/html\" data=\"readme-\1plotly.html\" style=\"width:100%;height:420px;\"></object>\n```")
     text_index = replace(text_index, r"```\n!\[\]\(docs/src/img/(.*?)\.png\)" => s"savefig(\"readme-\1.png\") # hide\nnothing # hide\n```\n![](readme-\1.png)")
diff --git a/docs/src/math/refinement.md b/docs/src/math/refinement.md
index ef555e01..2300d59a 100644
--- a/docs/src/math/refinement.md
+++ b/docs/src/math/refinement.md
@@ -27,8 +27,8 @@ nothing # hide
 
 ![](refinement_2dim_original.png)
 
-### h-refinement
-Insert additional knots to knot vector without changing the shape.
+### h-refinement (knot insertion)
+Insert additional knots to knot vectors without changing the shape.
 
 ```@repl math_refinement
 k₊ = (KnotVector([3.3,4.2]), KnotVector([3.8,3.2,5.3])) # additional knot vectors
@@ -40,8 +40,8 @@ nothing # hide
 
 ![](refinement_2dim_h.png)
 
-### p-refinement
-Increase the polynomial degree of B-spline manifold without changing the shape.
+### p-refinement (degree elevation)
+Increase the polynomial degrees of B-spline manifold without changing the shape.
 
 ```@repl math_refinement
 p₊ = (Val(1), Val(2)) # additional degrees