diff --git a/docs/chapter4/img/4.1.png b/docs/chapter4/img/4.1.png
deleted file mode 100644
index 6e8519f..0000000
Binary files a/docs/chapter4/img/4.1.png and /dev/null differ
diff --git a/docs/chapter4/img/4.10.png b/docs/chapter4/img/4.10.png
deleted file mode 100644
index 52d050b..0000000
Binary files a/docs/chapter4/img/4.10.png and /dev/null differ
diff --git a/docs/chapter4/img/4.11.png b/docs/chapter4/img/4.11.png
deleted file mode 100644
index 4b4d507..0000000
Binary files a/docs/chapter4/img/4.11.png and /dev/null differ
diff --git a/docs/chapter4/img/4.12.png b/docs/chapter4/img/4.12.png
deleted file mode 100644
index e6ddcf4..0000000
Binary files a/docs/chapter4/img/4.12.png and /dev/null differ
diff --git a/docs/chapter4/img/4.13.png b/docs/chapter4/img/4.13.png
deleted file mode 100644
index 203d2a7..0000000
Binary files a/docs/chapter4/img/4.13.png and /dev/null differ
diff --git a/docs/chapter4/img/4.14.png b/docs/chapter4/img/4.14.png
deleted file mode 100644
index 3069eee..0000000
Binary files a/docs/chapter4/img/4.14.png and /dev/null differ
diff --git a/docs/chapter4/img/4.15.png b/docs/chapter4/img/4.15.png
deleted file mode 100644
index 78b2c45..0000000
Binary files a/docs/chapter4/img/4.15.png and /dev/null differ
diff --git a/docs/chapter4/img/4.16.png b/docs/chapter4/img/4.16.png
deleted file mode 100644
index 3a35bc3..0000000
Binary files a/docs/chapter4/img/4.16.png and /dev/null differ
diff --git a/docs/chapter4/img/4.17.png b/docs/chapter4/img/4.17.png
deleted file mode 100644
index 770a694..0000000
Binary files a/docs/chapter4/img/4.17.png and /dev/null differ
diff --git a/docs/chapter4/img/4.18.png b/docs/chapter4/img/4.18.png
deleted file mode 100644
index 5e2caf8..0000000
Binary files a/docs/chapter4/img/4.18.png and /dev/null differ
diff --git a/docs/chapter4/img/4.19.png b/docs/chapter4/img/4.19.png
deleted file mode 100644
index 488258f..0000000
Binary files a/docs/chapter4/img/4.19.png and /dev/null differ
diff --git a/docs/chapter4/img/4.2.png b/docs/chapter4/img/4.2.png
deleted file mode 100644
index 6250af6..0000000
Binary files a/docs/chapter4/img/4.2.png and /dev/null differ
diff --git a/docs/chapter4/img/4.20.png b/docs/chapter4/img/4.20.png
deleted file mode 100644
index 8284e0a..0000000
Binary files a/docs/chapter4/img/4.20.png and /dev/null differ
diff --git a/docs/chapter4/img/4.21.png b/docs/chapter4/img/4.21.png
deleted file mode 100644
index 815c2f7..0000000
Binary files a/docs/chapter4/img/4.21.png and /dev/null differ
diff --git a/docs/chapter4/img/4.22.png b/docs/chapter4/img/4.22.png
deleted file mode 100644
index 159e250..0000000
Binary files a/docs/chapter4/img/4.22.png and /dev/null differ
diff --git a/docs/chapter4/img/4.23.png b/docs/chapter4/img/4.23.png
deleted file mode 100644
index 5fb2d68..0000000
Binary files a/docs/chapter4/img/4.23.png and /dev/null differ
diff --git a/docs/chapter4/img/4.24.png b/docs/chapter4/img/4.24.png
deleted file mode 100644
index 84bee8d..0000000
Binary files a/docs/chapter4/img/4.24.png and /dev/null differ
diff --git a/docs/chapter4/img/4.25.png b/docs/chapter4/img/4.25.png
deleted file mode 100644
index 0df35c8..0000000
Binary files a/docs/chapter4/img/4.25.png and /dev/null differ
diff --git a/docs/chapter4/img/4.26.png b/docs/chapter4/img/4.26.png
deleted file mode 100644
index b4216a1..0000000
Binary files a/docs/chapter4/img/4.26.png and /dev/null differ
diff --git a/docs/chapter4/img/4.27.png b/docs/chapter4/img/4.27.png
deleted file mode 100644
index bf3c2bc..0000000
Binary files a/docs/chapter4/img/4.27.png and /dev/null differ
diff --git a/docs/chapter4/img/4.28.png b/docs/chapter4/img/4.28.png
deleted file mode 100644
index 2a49c0c..0000000
Binary files a/docs/chapter4/img/4.28.png and /dev/null differ
diff --git a/docs/chapter4/img/4.3.png b/docs/chapter4/img/4.3.png
deleted file mode 100644
index cca153f..0000000
Binary files a/docs/chapter4/img/4.3.png and /dev/null differ
diff --git a/docs/chapter4/img/4.4.png b/docs/chapter4/img/4.4.png
deleted file mode 100644
index 9f0233f..0000000
Binary files a/docs/chapter4/img/4.4.png and /dev/null differ
diff --git a/docs/chapter4/img/4.5.png b/docs/chapter4/img/4.5.png
deleted file mode 100644
index d553434..0000000
Binary files a/docs/chapter4/img/4.5.png and /dev/null differ
diff --git a/docs/chapter4/img/4.6.png b/docs/chapter4/img/4.6.png
deleted file mode 100644
index 825f92a..0000000
Binary files a/docs/chapter4/img/4.6.png and /dev/null differ
diff --git a/docs/chapter4/img/4.7.png b/docs/chapter4/img/4.7.png
deleted file mode 100644
index 52de9f8..0000000
Binary files a/docs/chapter4/img/4.7.png and /dev/null differ
diff --git a/docs/chapter4/img/4.8.png b/docs/chapter4/img/4.8.png
deleted file mode 100644
index 62f994a..0000000
Binary files a/docs/chapter4/img/4.8.png and /dev/null differ
diff --git a/docs/chapter4/img/4.9.png b/docs/chapter4/img/4.9.png
deleted file mode 100644
index 22a2c52..0000000
Binary files a/docs/chapter4/img/4.9.png and /dev/null differ