Klein, Daniel, Christopher Ludwig and Christoph Spengel (2022), Taxing the Digital Economy: Investor Reaction to the European Commission's Digital Tax Proposals, National Tax Journal.

Lüdemann, Niklas, Ageda Shiba, Nikolaos Thymianis, Nicolas Heist, Christopher Ludwig and Heiko Paulheim (2020), A Knowledge Graph for Assessing Agressive Tax Planning Strategies, The Semantic Web – ISWC 2020 2, 395-410.

Klein, Daniel, Christopher Ludwig and Christoph Spengel (2020), Besteuerung digitaler Unternehmen – die schwierige Suche nach einem europäischen Ansatz, integration Jahrgang 43, Heft 3, 169–185.

Dutt, Verena, Christopher Ludwig, Katharina Nicolay, Heiko Vay and Johannes Voget (2019), Increasing Tax Transparency: Investor Reactions to the Country-by-Country Reporting Requirement for EU Financial Institutions, International Tax and Public Finance 26 (6), 1259-1290.

Spengel, Christoph and Christopher Ludwig (2019), Profit Allocation in Digital Businesses, TPI - Transfer Pricing International 5 , 258-262.

Spengel, Christoph and Christopher Ludwig (2021), Taxing the Digital Economy – An Academic Perspective, in: BDI – Federation of German Industries BDI Position, Berlin, 18-23

Spengel, Christoph and Christopher Ludwig (2021), Besteuerung digitaler Unternehmen - Geschäftsmodelle im Wandel und aktuelle Reformvorschläge, in: Norbert Herzig, Guideo Förster, Arne Schnitger, Christian Levedag München,

Ludwig, Christopher, Marcel Olbert and Christoph Spengel (2019), Transfer Pricing for Data Businesses: How to Apply the Arm's Length Principle to the Digital Economy, in: Pasquale Pistone and Dennis Weber Amsterdam, 27-47

Spengel, Christoph, Leonie Fischer, Christopher Ludwig, Jessica Müller, Stefan Weck and Sarah Winter (2021), Debt-Equity Bias Should Be Addressed on National Rather Than on EU Level, ZEW policy brief No. 21-07, Mannheim

Spengel, Christoph, Daniel Klein, Christopher Ludwig, Jessica Müller, Raphael Müller, Stefan Weck and Sarah Winter (2021), EU Should Focus more on Indirect Taxes Instead of Proposals for a Digital Levy, ZEW policy brief No. 21-02, Mannheim

Klein, Daniel, Christopher Ludwig, Katharina Nicolay and Christoph Spengel (2021), Quantifying the OECD BEPS Indicators – an Update to BEPS Action 11, ZEW Discussion Paper No. 21-013, Mannheim

Klein, Daniel, Christopher Ludwig and Katharina Nicolay (2020), Internal Digitalization and Tax-Efficient Decision Making, ZEW Discussion Paper No. 20-051, Mannheim

Lüdemann, Niklas, Ageda Shiba, Nikolaos Thymianis, Nicolas Heist, Christopher Ludwig and Heiko Paulheim (2020), A Knowledge Graph for Assessing Agressive Tax Planning Strategies, Mannheim.

Spengel, Christoph, Christopher Ludwig, Raphael Müller and Ann-Catherin Werner (2020), Sharing Economy – Steuerliche Herausforderungen und Lösungsansätze, ZEW policy brief No. 20-03, Mannheim

Fischer, Leonie, Daniel Klein, Christopher Ludwig, Raphael Müller and Christoph Spengel (2020), Global Corporate Tax Reform to the Worse? Assessing the OECD Proposals, ZEW policy brief No. 20-01, Mannheim

Bräutigam, Rainer, Christopher Ludwig and Christoph Spengel (2019), Steuerlicher Reformbedarf bei Service-Plattformen, ZEW expert brief No. 19-01, Mannheim

Klein, Daniel, Christopher Ludwig and Christoph Spengel (2019), Ring-Fencing Digital Corporations: Investor Reaction to the European Commission’s Digital Tax Proposals, ZEW Discussion Paper No. 19-050, Mannheim

Spengel, Christoph, Frank Schmidt, Jost Henrich Heckemeyer, Katharina Nicolay, Alexandra Bartholmeß, Christopher Ludwig, Daniela Steinbrenner, Peter Buchmann, Theresa Bührle, Verena Dutt, Leonie Fischer, Julia Spix and Barbara Stage (2021), Effective Tax Levels Using the Devereux/Griffith Methodology - Update 2020, EU Commission , Mannheim

Spengel, Christoph, Frank Schmidt, Jost Henrich Heckemeyer, Katharina Nicolay, Alexandra Bartholmeß, Christopher Ludwig, Daniela Steinbrenner, Peter Buchmann, Theresa Bührle, Verena Dutt, Leonie Fischer and Barbara Stage (2020), Effective Tax Levels Using the Devereux/Griffith Methodology - Update 2019, EU Commission , Mannheim

Spengel, Christoph, Frank Schmidt, Jost Henrich Heckemeyer, Katharina Nicolay, Alexandra Bartholmeß, Christopher Ludwig, Daniela Steinbrenner, Rainer Bräutigam, Peter Buchmann, Theresa Bührle, Elisa Casi, Verena Dutt, Leonie Fischer, Christoph Harendt, Raphael Müller, Thomas Schwab, Barbara Stage, Heiko Vay and Ann-Catherin Werner (2019), Effective Tax Levels Using the Devereux/Griffith Methodology - Update 2018, Project for the EU Commission TAXUD/2018/DE/307 Intermediary Report 2018 , Mannheim

Bräutigam, Rainer, Christopher Ludwig and Christoph Spengel (2019), Studie zur Steuervermeidung von Konzernen weist gravierende methodische Mängel auf, Mannheim

Bräutigam, Rainer, Christopher Ludwig and Christoph Spengel (2019), Steuerlicher Reformbedarf bei Service-Plattformen, Mannheim