Update README.

README.md

@@ -36,7 +36,7 @@ Selections are immutable. All selection methods that affect which elements are s
 
 ## Installing
 
-If you use NPM, `npm install d3-selection`. Otherwise, download the [latest release](https://github.com/d3/d3-selection/releases/latest). You can also load directly from [d3js.org](https://d3js.org), either as a [standalone library](https://d3js.org/d3-selection.v1.min.js) or as part of [D3 4.0](https://github.com/d3/d3). AMD, CommonJS, and vanilla environments are supported. In vanilla, a `d3` global is exported:
+If you use NPM, `npm install d3-selection`. Otherwise, download the [latest release](https://github.com/d3/d3-selection/releases/latest). You can also load directly from [d3js.org](https://d3js.org), either as a [standalone library](https://d3js.org/d3-selection.v1.min.js) or as part of [D3](https://github.com/d3/d3). AMD, CommonJS, and vanilla environments are supported. In vanilla, a `d3` global is exported:
 
 ```html
 <script src="https://d3js.org/d3-selection.v1.min.js"></script>
@@ -47,7 +47,7 @@ const div = d3.selectAll("div");
 </script>
 ```
 
-[Try d3-selection in your browser.](https://tonicdev.com/npm/d3-selection)
+[Try d3-selection in your browser.](https://observablehq.com/collection/@d3/d3-selection)
 
 ## API Reference