lesson 26 nouns, and inter-lesson links

docs/howtostudykorean/unit-1/07-irregulars.md

@@ -2328,7 +2328,7 @@ When adding ~ㄴ/은 to a stem which ends in ㄹ, the ㄹ is removed and ㄴ is
 - 멀 + ㄴ = <TTS>먼</TTS>
 - 저는 먼 병원에 갔어요 <AudioButton src="https://www.howtostudykorean.com/wp-content/uploads/2013/05/21-I-went-to-a-far-away-hospital.mp3" /> = <span class="md spoiler">I went to a far away hospital (a hospital that is far away)</span>
 
-There will be times when you have to add ~ㄴ/은 to verbs stems as well, but you haven’t learned about this yet. I introduce this concept in [Lesson 26](https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-26-33/lesson-26/), and then talk about the irregular being applied in [Lesson 28](https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-26-33/lesson-28/). I don’t want you to think about this too much until those lessons, but just so you know, the concept is the same as adding ~ㄴ/은 to an adjective. For example:
+There will be times when you have to add ~ㄴ/은 to verbs stems as well, but you haven’t learned about this yet. I introduce this concept in [Lesson 26](../unit-2/26-describing-nouns-with-verbs.md), and then talk about the irregular being applied in [Lesson 28](https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-26-33/lesson-28/). I don’t want you to think about this too much until those lessons, but just so you know, the concept is the same as adding ~ㄴ/은 to an adjective. For example:
 
 - 열다 = <span class="md spoiler">to open</span>
   - 열 + ㄴ = <TTS>연</TTS>
@@ -2471,7 +2471,7 @@ This same idea can be applied to grammatical additions that will be introduced i
 Each time a new format/style of addition is introduced in my lessons, I will explain how irregulars adapt to it. This only needs to be done once for each format, because each successive addition with the same format will create the same change to irregulars. Below is a list of grammatical principles you will learn in future lessons. Each one follows a particular style. In each of these lessons, I will explain how they cause irregular words to change. Furthermore, I will explain the other grammatical principles that follow the same format that will create the same change:
 
 - ~ㄹ/을 ([Lesson 9](./09-conjugate-이다.md))
-- ~니 ([Lesson 21](https://www.howtostudykorean.com/unit1/unit-1-lessons-17-25-2/lesson-21-asking-questions-in-korean-why-when-where-and-who/))
+- ~니 ([Lesson 21](./21-why-when-where-who.md))
 - ~ㅁ/음 ([Lesson 29](https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-26-33/lesson-29/))
 - ~(으)려고 ([Lesson 32](https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-26-33/lesson-32/))
 - ~(으)시다 ([Lesson 39](https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-34-41/lesson-39/))