1 files changed, 4 insertions, 0 deletions
diff --git a/01-19.md b/01-19.md
index 5b32d08..a7340f7 100644
--- a/01-19.md
+++ b/01-19.md
@@ -513,3 +513,7 @@ void bag::operator +=(const bag& addend){
 	- The array
 	- A variable to keep track of how much of the array is being used
 - At the top of the implementation file: When you design a class, always make an explicit statement of the rules (**invariant of the class**) that dictate how the member variables are used
+
+---
+
+[01/21 ->](01-21.md)