diff --git a/book/_ext/apastyle.py b/book/_ext/apastyle.py
new file mode 100644
index 0000000..16828fe
--- /dev/null
+++ b/book/_ext/apastyle.py
@@ -0,0 +1,17 @@
+
+# from pybtex.style.formatting.unsrt import Style
+from pybtexapastyle.formatting.apa import APAStyle
+from pybtexapastyle.labels.apa import LabelStyle as APALabelStyle
+from pybtex.plugin import register_plugin
+# from pybtex.style.template import names, sentence
+
+class MyAPALabelStyle(APALabelStyle):
+    def format_label(self, entry):
+        return APALabelStyle.format_label(self, entry)
+
+class MyAPAStyle(APAStyle):
+    default_label_style = 'myapa'
+
+def setup(app):
+    register_plugin('pybtex.style.labels', 'myapa', MyAPALabelStyle)
+    register_plugin('pybtex.style.formatting', 'myapastyle', MyAPAStyle)
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diff --git a/book/_ext/bracket_citation_style.py b/book/_ext/bracket_citation_style.py
new file mode 100644
index 0000000..cab10f3
--- /dev/null
+++ b/book/_ext/bracket_citation_style.py
@@ -0,0 +1,27 @@
+from dataclasses import dataclass, field
+import sphinxcontrib.bibtex.plugin
+
+from sphinxcontrib.bibtex.style.referencing import BracketStyle
+from sphinxcontrib.bibtex.style.referencing.author_year import AuthorYearReferenceStyle
+
+
+def bracket_style() -> BracketStyle:
+    return BracketStyle(
+        left='(',
+        right=')',
+    )
+
+
+@dataclass
+class MyReferenceStyle(AuthorYearReferenceStyle):
+    bracket_parenthetical: BracketStyle = field(default_factory=bracket_style)
+    bracket_textual: BracketStyle = field(default_factory=bracket_style)
+    bracket_author: BracketStyle = field(default_factory=bracket_style)
+    bracket_label: BracketStyle = field(default_factory=bracket_style)
+    bracket_year: BracketStyle = field(default_factory=bracket_style)
+
+
+def setup(app):
+    sphinxcontrib.bibtex.plugin.register_plugin(
+        'sphinxcontrib.bibtex.style.referencing',
+        'author_year_round', MyReferenceStyle)
\ No newline at end of file