[css-ruby] Flesh out the introduction to supplementary material

Author: frivoal

css-ruby-1/Overview.bs

@@ -84,13 +84,21 @@ What is ruby?</h3>
 		correctly paired with their respective base characters.
 	</div>
 
-	[=Ruby=] formatting as used in Japanese is described in JIS X-4051 [[JIS4051]] (in Japanese)
-	and in Requirements for Japanese Text Layout [[JLREQ]] (in English and Japanese)].
 	In HTML, ruby structure and markup to represent it is described
 	in the Ruby Markup Extension specification.
 	This module describes the CSS rendering model
 	and formatting controls relevant to ruby layout of such markup.
 
+	A more in-depth introduction to [=Ruby=] and its formatting
+	can be found in the “What is Ruby“ article [[QA-RUBY]].
+	Extensive information about the main ways [=ruby=] has traditionally been formatted in Japanese
+	can be found in JIS X-4051 [[JIS4051]] (in Japanese)
+	and in <a href="https://www.w3.org/TR/jlreq/#ruby_and_emphasis_dots">“Ruby and Emphasis Dots”</a> in <cite>Requirements for Japanese Text Layout</cite> [[JLREQ]] (in English and Japanese);
+	<cite>Rules for Simple Placement of Japanese Ruby</cite> [[SIMPLE-RUBY]]
+	also describes (in English) one possible approach for Japanese ruby formatting.
+	<a href="https://www.w3.org/TR/clreq/#interlinear_annotations">“Interlinear annotations”</a> in <cite>Requirements for Chinese Text Layout</cite> [[CLREQ]]
+	describes the related practices for Chinese typography (in Chinese and English).
+
 <h3 id="placement">
 Module interactions</h3>