diff --git a/package-lock.json b/package-lock.json
index 371d18635..782506944 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2169,9 +2169,9 @@
       }
     },
     "@stencila/encoda": {
-      "version": "0.90.3",
-      "resolved": "https://registry.npmjs.org/@stencila/encoda/-/encoda-0.90.3.tgz",
-      "integrity": "sha512-gOn+MfLqOAA4tP1mah7mshvnknCGFWNea3zJTAH/DKLHr3vLYoy6yCZyWBApAqDbUd/dF2y22qCkj6fLmFFWEQ==",
+      "version": "0.91.0",
+      "resolved": "https://registry.npmjs.org/@stencila/encoda/-/encoda-0.91.0.tgz",
+      "integrity": "sha512-/reictGr+iaNNOO9RI2ESdmzAIeMUlUm1yUV1byho4QYi4YWye0clMsF/njO6Vv462N+IhN2YIZLHJGAdlkIjQ==",
       "dev": true,
       "requires": {
         "@stencila/executa": "^1.9.2",
@@ -2398,9 +2398,9 @@
           "dev": true
         },
         "minimist": {
-          "version": "1.2.4",
-          "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.4.tgz",
-          "integrity": "sha512-wTiNDqe4D2rbTJGZk1qcdZgFtY0/r+iuE6GDT7V0/+Gu5MLpIDm4+CssDECR79OJs/OxLPXMzdxy153b5Qy3hg==",
+          "version": "1.2.5",
+          "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
+          "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw==",
           "dev": true
         },
         "p-cancelable": {
@@ -2779,9 +2779,9 @@
       }
     },
     "@stencila/thema": {
-      "version": "1.14.2",
-      "resolved": "https://registry.npmjs.org/@stencila/thema/-/thema-1.14.2.tgz",
-      "integrity": "sha512-7xQkGTCMF1YJKR38MjEFkNk/87GswFg3HaYPFJAb4q8cGgMpKVPpH42UAe0hEKBXq1B/JSWuBhjjZHDHVbVcTg==",
+      "version": "1.15.0",
+      "resolved": "https://registry.npmjs.org/@stencila/thema/-/thema-1.15.0.tgz",
+      "integrity": "sha512-/CMbMWHU6hR5wu0gSKNVmjkCgow+TiUsbyxdSblvKrQSKu+Ry0E8cZW4V7VuRXfvmpf6lOqUQzK0qq5aebvF0w==",
       "dev": true,
       "requires": {
         "@simonwep/pickr": "^1.5.1",
@@ -7534,9 +7534,9 @@
       "dev": true
     },
     "cfb": {
-      "version": "1.1.3",
-      "resolved": "https://registry.npmjs.org/cfb/-/cfb-1.1.3.tgz",
-      "integrity": "sha512-joXBW0nMuwV9no7UTMiyVJnQL6XIU3ThXVjFUDHgl9MpILPOomyfaGqC290VELZ48bbQKZXnQ81UT5HouTxHsw==",
+      "version": "1.1.4",
+      "resolved": "https://registry.npmjs.org/cfb/-/cfb-1.1.4.tgz",
+      "integrity": "sha512-rwFkl3aFO3f+ljR27YINwC0x8vPjyiEVbYbrTCKzspEf7Q++3THdfHVgJYNUbxNcupJECrLX+L40Mjm9hm/Bgw==",
       "dev": true,
       "requires": {
         "adler-32": "~1.2.0",
diff --git a/package.json b/package.json
index e87dbc1b0..e34f96e72 100644
--- a/package.json
+++ b/package.json
@@ -63,7 +63,7 @@
   },
   "devDependencies": {
     "@stencila/dev-config": "1.4.20",
-    "@stencila/encoda": "^0.90.3",
+    "@stencila/encoda": "0.91.0",
     "@stencila/schema": "0.41.2",
     "@types/jest": "25.1.4",
     "@types/prismjs": "1.16.0",
diff --git a/src/extensions/cite-apa/index.ts b/src/extensions/cite-apa/index.ts
index 7b13b6847..8f4901213 100644
--- a/src/extensions/cite-apa/index.ts
+++ b/src/extensions/cite-apa/index.ts
@@ -1,4 +1,3 @@
-import '../cite'
 import { ready, select, text } from '../../util'
 
 /**
diff --git a/src/extensions/cite-mla/index.ts b/src/extensions/cite-mla/index.ts
deleted file mode 100644
index 9bf2f6dfa..000000000
--- a/src/extensions/cite-mla/index.ts
+++ /dev/null
@@ -1 +0,0 @@
-import '../cite'
diff --git a/src/extensions/cite/index.test.ts b/src/extensions/cite/index.test.ts
deleted file mode 100644
index a0fe2470a..000000000
--- a/src/extensions/cite/index.test.ts
+++ /dev/null
@@ -1,35 +0,0 @@
-import { whenReady, select } from '../../util'
-
-const body = document.body
-
-test('DOM manipulations', async () => {
-  body.innerHTML = `
-<section data-itemprop="references">
-  <ol>
-    <li itemscope="" itemtype="http://schema.org/Article" id="bib1" itemprop="citation">
-      <div itemscope="" itemtype="http://schema.org/Organization" itemprop="publisher">
-        <meta itemprop="name" content="Unknown">
-        <div itemscope="" itemtype="http://schema.org/ImageObject" itemprop="logo">
-          <meta itemprop="url" content="https://via.placeholder.com/" src="https://via.placeholder.com/">
-        </div>
-      </div><span itemprop="headline">The continuing case for the Renshaw cell</span>
-      <meta itemprop="image" content="https://via.placeholder.com/">
-      <ol data-itemprop="authors">
-        <li itemscope="" itemtype="http://schema.org/Person" itemprop="author"><span itemprop="name" content="FJ Alvarez"><span itemprop="givenName">FJ</span><span itemprop="familyName">Alvarez</span></span></li>
-        <li itemscope="" itemtype="http://schema.org/Person" itemprop="author"><span itemprop="name" content="REW Fyffe"><span itemprop="givenName">REW</span><span itemprop="familyName">Fyffe</span></span></li>
-      </ol><span>
-        <meta itemprop="datePublished" content="2007"><time datetime="2007" itemscope="" itemtype="http://schema.org/Date">2007</time></span>
-    </li>
-  </ol>
-</section>
-  `
-
-  await import('.')
-  whenReady()
-
-  expect(select('ol:--authors').length).toBe(0)
-  expect(select('span:--authors').length).toBe(1)
-
-  expect(select('li:--author').length).toBe(0)
-  expect(select('span:--author').length).toBe(2)
-})
diff --git a/src/extensions/cite/index.ts b/src/extensions/cite/index.ts
deleted file mode 100644
index c74c723aa..000000000
--- a/src/extensions/cite/index.ts
+++ /dev/null
@@ -1,18 +0,0 @@
-import { ready, replace, select, tag } from '../../util'
-
-ready(() =>
-  select(':--references :--reference').forEach(reference => {
-    // Change `authors` property from list to nested spans
-    select(reference, 'ol:--authors').forEach(authors => {
-      select(authors, 'li:--author').forEach(author =>
-        replace(author, tag(author, 'span'))
-      )
-      return replace(authors, tag(authors, 'span'))
-    })
-
-    // If `publisher` is a div make it a span
-    select(reference, 'div:--publisher').forEach(elem =>
-      replace(elem, tag(elem, 'span'))
-    )
-  })
-)
diff --git a/src/extensions/headings/README.md b/src/extensions/headings/README.md
deleted file mode 100644
index 476f5d39b..000000000
--- a/src/extensions/headings/README.md
+++ /dev/null
@@ -1,5 +0,0 @@
-# Headings extension
-
-A temporary extensions that changes the way that `Heading` nodes are represented. Ensures that there is only one `<h1>` tag (for the `title` property) and that `Heading` nodes are represented as `<h${depth+1}>`.
-
-See https://github.com/stencila/encoda/issues/443.
diff --git a/src/extensions/headings/index.test.ts b/src/extensions/headings/index.test.ts
deleted file mode 100644
index c0dfe5e1f..000000000
--- a/src/extensions/headings/index.test.ts
+++ /dev/null
@@ -1,43 +0,0 @@
-import { whenReady, select, text, first } from '../../util'
-
-const body = document.body
-
-test('DOM manipulations', async () => {
-  body.innerHTML = `
-    <h1>The title</h1>
-    <h2 data-itemtype="http://schema.stenci.la/Heading">Abstract</h2>
-
-    <h1 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 1</h1>
-    <h2 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 2</h2>
-    <h3 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 3</h3>
-    <h4 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 4</h4>
-    <h5 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 5</h5>
-    <h6 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 6</h6>
-  `
-
-  await import('.')
-  whenReady()
-
-  expect(body.innerHTML).toEqual(`
-    <h1>The title</h1>
-    <h2 data-itemtype="http://schema.stenci.la/Heading">Abstract</h2>
-
-    <h2 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 1</h2>
-    <h3 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 2</h3>
-    <h4 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 3</h4>
-    <h5 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 4</h5>
-    <h6 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 5</h6>
-    <h6 itemscope="" itemtype="http://schema.stenci.la/Heading">Heading 6</h6>
-  `)
-
-  expect(text(first('h1') ?? body)).toBe('The title')
-  expect(text(first('h2[data-itemtype]') ?? body)).toBe('Abstract')
-
-  expect(text(first('h2[itemtype]') ?? body)).toBe('Heading 1')
-  expect(text(first('h3[itemtype]') ?? body)).toBe('Heading 2')
-  expect(text(first('h4[itemtype]') ?? body)).toBe('Heading 3')
-  expect(text(first('h5[itemtype]') ?? body)).toBe('Heading 4')
-  const h6s = select('h6[itemtype]')
-  expect(text(h6s[0])).toBe('Heading 5')
-  expect(text(h6s[1])).toBe('Heading 6')
-})
diff --git a/src/extensions/headings/index.ts b/src/extensions/headings/index.ts
deleted file mode 100644
index dbcbf2920..000000000
--- a/src/extensions/headings/index.ts
+++ /dev/null
@@ -1,16 +0,0 @@
-import { select, ready, tag, replace } from '../../util'
-
-/**
- * Find all heading nodes and change their depth to depth +1
- *
- * Currently, there are some "presentational" <h2> nodes added with
- * `data-itemtype` e.g `<h2 data-itemtype="http://schema.stenci.la/Heading">Abstract</h2>`.
- * These are not selected when using `:--Heading`.
- */
-ready(() => {
-  select(':--Heading').forEach(heading => {
-    const level = parseFloat(/^H([1-6])$/.exec(heading.tagName)?.[1] ?? '0')
-    const newLevel = Math.min(level + 1, 6)
-    replace(heading, tag(heading, `h${newLevel}`))
-  })
-})
diff --git a/src/extensions/headings/styles.css b/src/extensions/headings/styles.css
deleted file mode 100644
index a716ef723..000000000
--- a/src/extensions/headings/styles.css
+++ /dev/null
@@ -1 +0,0 @@
-/* Add your extension's styles to this file */
diff --git a/src/extensions/math/index.ts b/src/extensions/math/index.ts
deleted file mode 100644
index 41e7ea6f8..000000000
--- a/src/extensions/math/index.ts
+++ /dev/null
@@ -1,3 +0,0 @@
-// No need for any Javascript. See README.md for why.
-
-export {}
diff --git a/src/extensions/pages/index.ts b/src/extensions/pages/index.ts
deleted file mode 100644
index dd061ecd0..000000000
--- a/src/extensions/pages/index.ts
+++ /dev/null
@@ -1,3 +0,0 @@
-// Do any initialization that your extension requires here.
-
-export {}
diff --git a/src/extensions/person/index.ts b/src/extensions/person/index.ts
deleted file mode 100644
index e8c285ebf..000000000
--- a/src/extensions/person/index.ts
+++ /dev/null
@@ -1,3 +0,0 @@
-// No need for any Javascript.
-
-export {}
diff --git a/src/themes/nature/index.ts b/src/themes/nature/index.ts
index 5cc3c9c2a..c679e6329 100644
--- a/src/themes/nature/index.ts
+++ b/src/themes/nature/index.ts
@@ -1,3 +1 @@
-import '../../extensions/math'
 import '../../extensions/code'
-import '../../extensions/person'
diff --git a/src/themes/plos/index.ts b/src/themes/plos/index.ts
index 5cc3c9c2a..c679e6329 100644
--- a/src/themes/plos/index.ts
+++ b/src/themes/plos/index.ts
@@ -1,3 +1 @@
-import '../../extensions/math'
 import '../../extensions/code'
-import '../../extensions/person'
diff --git a/src/themes/rpng/index.ts b/src/themes/rpng/index.ts
index 17ea2e312..336ce12bb 100644
--- a/src/themes/rpng/index.ts
+++ b/src/themes/rpng/index.ts
@@ -1 +1 @@
-import '../../extensions/math'
+export {}
diff --git a/src/themes/skeleton/index.ts b/src/themes/skeleton/index.ts
index 1bf767e2c..7a203438c 100644
--- a/src/themes/skeleton/index.ts
+++ b/src/themes/skeleton/index.ts
@@ -1,5 +1,2 @@
 import '../../extensions/cite-apa'
 import '../../extensions/code'
-import '../../extensions/math'
-import '../../extensions/pages'
-import '../../extensions/person'