diff --git a/pyproject.toml b/pyproject.toml
index 13b49ec..bd8ca4c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -14,7 +14,6 @@ dependencies = [
     "pydantic~=2.10.6",
     "requests~=2.32.3",
     "typer[all]~=0.9.0",
-    "xlsxwriter~=3.2.0",
 ]
 requires-python = ">=3.9"
 classifiers = [
diff --git a/src/bibx/algorithms/preprocess.py b/src/bibx/algorithms/preprocess.py
deleted file mode 100644
index 48598f1..0000000
--- a/src/bibx/algorithms/preprocess.py
+++ /dev/null
@@ -1,233 +0,0 @@
-"""Algorithms for preprocessing the data."""
-
-from typing import Optional
-
-from xlsxwriter import Workbook
-from xlsxwriter.worksheet import Worksheet
-
-from bibx.collection import Collection
-
-from .sap import BRANCH, LEAF, ROOT, TRUNK, Sap
-
-
-class Preprocess:
-    """Preprocess the data."""
-
-    def __init__(self, wos: Collection, scopus: Collection) -> None:
-        self.wos = wos
-        self.scopus = scopus
-        self._merged: Optional[Collection] = None
-
-    @property
-    def merged(self) -> Collection:
-        """Merge the collections."""
-        if self._merged is None:
-            self._merged = self.wos.merge(self.scopus)
-        return self._merged
-
-    def __repr__(self) -> str:
-        """Return the representation of the object."""
-        return f"{self.__class__.__name__}(wos={self.wos}, scopus={self.scopus})"
-
-    def _write_collection_to_workseet(
-        self,
-        collection: Collection,
-        workseet: Worksheet,
-    ) -> None:
-        for i, title in enumerate(
-            [
-                "Authors",
-                "Year",
-                "Title",
-                "Journal",
-                "Volume",
-                "Issue",
-                "Page",
-                "DOI",
-                "Times Cited",
-                "Label",
-            ]
-        ):
-            workseet.write(0, i, title)
-
-        for i, row in enumerate(collection.articles, start=1):
-            workseet.write(i, 0, "; ".join(row.authors))
-            workseet.write(i, 1, row.year)
-            workseet.write(i, 2, row.title)
-            workseet.write(i, 3, row.journal)
-            workseet.write(i, 4, row.volume)
-            workseet.write(i, 5, row.issue)
-            workseet.write(i, 6, row.page)
-            workseet.write(i, 7, row.doi)
-            workseet.write(i, 8, row.times_cited)
-            workseet.write(i, 9, row.label)
-
-    def write_merged_information(self, workseet: Worksheet) -> None:
-        """Write the merged information to a worksheet."""
-        self._write_collection_to_workseet(self.merged, workseet)
-
-    def write_wos_information(self, workseet: Worksheet) -> None:
-        """Write the WOS information to a worksheet."""
-        self._write_collection_to_workseet(self.wos, workseet)
-
-    def write_scopus_information(self, workseet: Worksheet) -> None:
-        """Write the Scopus information to a worksheet."""
-        self._write_collection_to_workseet(self.scopus, workseet)
-
-    def write_reference_information(self, workseet: Worksheet) -> None:
-        """Write the reference information to a worksheet."""
-        for i, title in enumerate(
-            [
-                "SR",
-                "SR_ref",
-                "Title",
-                "Authors",
-                "Journal",
-                "Year",
-                "Label",
-            ]
-        ):
-            workseet.write(0, i, title)
-        row = 1
-        for article in self.merged.articles:
-            for ref in article.references:
-                workseet.write(row, 0, article.label)
-                workseet.write(row, 1, ref.label)
-                workseet.write(row, 2, ref.title)
-                workseet.write(row, 3, "; ".join(ref.authors))
-                workseet.write(row, 4, ref.journal)
-                workseet.write(row, 5, ref.year)
-                workseet.write(row, 6, ref.label)
-                row += 1
-
-    def write_journal_information(self, workseet: Worksheet) -> None:
-        """Write the journal information to the worksheet."""
-        for i, title in enumerate(
-            [
-                "Label",
-                "Journal",
-                "Year",
-                "Cited Journal",
-                "Cited Year",
-            ]
-        ):
-            workseet.write(0, i, title)
-        row = 1
-        for article in self.merged.articles:
-            for ref in article.references:
-                workseet.write(row, 0, article.label)
-                workseet.write(row, 1, article.journal)
-                workseet.write(row, 2, article.year)
-                workseet.write(row, 3, ref.journal)
-                workseet.write(row, 4, ref.year)
-                row += 1
-
-    def write_author_information(self, workseet: Worksheet) -> None:
-        """Write the author information to the worksheet."""
-        for i, title in enumerate(
-            [
-                "Author",
-                "Year",
-                "Cited Author",
-                "Cited Year",
-            ]
-        ):
-            workseet.write(0, i, title)
-        row = 1
-        for article in self.merged.articles:
-            for ref in article.references:
-                for author in article.authors:
-                    for cited_author in ref.authors:
-                        workseet.write(row, 0, author)
-                        workseet.write(row, 1, article.year)
-                        workseet.write(row, 2, cited_author)
-                        workseet.write(row, 3, ref.year)
-                        row += 1
-
-    def write_times_cited_information(self, workseet: Worksheet) -> None:
-        """Write the times cited information to the worksheet."""
-        for i, title in enumerate(
-            [
-                "Year",
-                "Times Cited Sum",
-                "Times Cited Percentage",
-            ]
-        ):
-            workseet.write(0, i, title)
-        years = self.merged.cited_by_year()
-        total = sum(years.values())
-        for i, (year, times_cited) in enumerate(years.items(), start=1):
-            workseet.write(i, 0, year)
-            workseet.write(i, 1, times_cited)
-            workseet.write(i, 2, times_cited / total)
-
-    @staticmethod
-    def _get_tos(data: dict) -> str:
-        if data[ROOT] > 0:
-            return "Root"
-        if data[TRUNK] > 0:
-            return "Trunk"
-        if data[LEAF] > 0:
-            return "Leaf"
-        if data[BRANCH] > 0:
-            return f"Branch {data[BRANCH]}"
-        return "_"
-
-    def write_tree_of_science_information(self, workseet: Worksheet) -> None:
-        """Write the tree of science information to the worksheet."""
-        s = Sap()
-        g = s.create_graph(self.merged)
-        g = s.clean_graph(g)
-        g = s.tree(g)
-
-        for i, title in enumerate(
-            [
-                "TOS",
-                "Label",
-                "Authors",
-                "Year",
-                "Title",
-                "Journal",
-                "Volume",
-                "Issue",
-                "Page",
-                "DOI",
-                "Times Cited",
-            ]
-        ):
-            workseet.write(0, i, title)
-
-        i = 1
-        for label, data in sorted(
-            g.nodes(data=True), key=lambda x: self._get_tos(x[1])
-        ):
-            tos = self._get_tos(data)
-            if tos == "_":
-                continue
-            workseet.write(i, 0, tos)
-            workseet.write(i, 1, label)
-            workseet.write(i, 2, "; ".join(data["authors"]))
-            workseet.write(i, 3, data["year"])
-            workseet.write(i, 4, data["title"])
-            workseet.write(i, 5, data["journal"])
-            workseet.write(i, 6, data["volume"])
-            workseet.write(i, 7, data["issue"])
-            workseet.write(i, 8, data["page"])
-            workseet.write(i, 9, data["doi"])
-            workseet.write(i, 10, data["times_cited"])
-            i += 1
-
-    def create_workbook(self, filename: str) -> None:
-        """Create a workbook with the information."""
-        workbook = Workbook(filename)
-        self.write_merged_information(workbook.add_worksheet("Merged"))
-        self.write_wos_information(workbook.add_worksheet("WOS"))
-        self.write_scopus_information(workbook.add_worksheet("Scopus"))
-        self.write_reference_information(workbook.add_worksheet("References"))
-        self.write_journal_information(workbook.add_worksheet("Journals"))
-        self.write_author_information(workbook.add_worksheet("Authors"))
-        self.write_times_cited_information(workbook.add_worksheet("Times Cited"))
-        self.write_tree_of_science_information(
-            workbook.add_worksheet("Tree of Science")
-        )
-        workbook.close()
diff --git a/src/bibx/cli.py b/src/bibx/cli.py
index 559c223..429d951 100644
--- a/src/bibx/cli.py
+++ b/src/bibx/cli.py
@@ -1,7 +1,5 @@
 import logging
-from collections.abc import Callable
 from enum import Enum
-from typing import TextIO
 
 import networkx as nx
 import typer
@@ -14,10 +12,8 @@
     read_scopus_ris,
     read_wos,
 )
-from bibx.algorithms.preprocess import Preprocess
 from bibx.algorithms.sap import Sap
 from bibx.builders.openalex import EnrichReferences
-from bibx.collection import Collection
 
 app = typer.Typer()
 
@@ -100,32 +96,5 @@ def openalex(
     rprint(graph)
 
 
-def _read_many(
-    reader: Callable[[TextIO], Collection],
-    *filenames: str,
-) -> Collection:
-    first, *rest = filenames
-    with open(first) as f:
-        collection = reader(f)
-    for filename in rest:
-        with open(filename) as f:
-            collection = collection.merge(reader(f))
-    return collection
-
-
-@app.command()
-def preprocess(
-    output: str,
-    wos: list[str] = typer.Option(help="WoS files to pre process"),
-    scopus: list[str] = typer.Option(help="scopus files to preprocess"),
-) -> None:
-    """Preprocesses a collection."""
-    wos_collection = _read_many(read_wos, *wos)
-    scopus_collection = _read_many(read_scopus_ris, *scopus)
-    p = Preprocess(wos_collection, scopus_collection)
-    p.create_workbook(output)
-    rprint(f":boom: workbook created at {output}")
-
-
 if __name__ == "__main__":
     app()
diff --git a/stubs/xlsxwriter/__init__.pyi b/stubs/xlsxwriter/__init__.pyi
deleted file mode 100644
index d34912f..0000000
--- a/stubs/xlsxwriter/__init__.pyi
+++ /dev/null
@@ -1,6 +0,0 @@
-from xlsxwriter.worksheet import Worksheet
-
-class Workbook:
-    def __init__(self, filename: str) -> None: ...
-    def add_worksheet(self, title: str) -> Worksheet: ...
-    def close(self) -> None: ...
diff --git a/stubs/xlsxwriter/worksheet.pyi b/stubs/xlsxwriter/worksheet.pyi
deleted file mode 100644
index 34fe6c8..0000000
--- a/stubs/xlsxwriter/worksheet.pyi
+++ /dev/null
@@ -1,8 +0,0 @@
-class Worksheet:
-    # NOTE: In reality, the write method has many overloads.
-    def write(
-        self,
-        row: int,
-        col: int,
-        value: int | float | str | None,
-    ) -> None: ...