Oja, Ahto (koost.) 1999. Eesti 21. sajandil: arengustrateegiad, visioonid, valikud. (Eessõnad: Mart Laar, Andres Tarand.) Tallinn: Teaduste Akadeemia Kirjastus. ISBN 9985-50-244-2
Oja, Ahto; Keerus, Külli; Järvik, Marek jt. 2003. Keskkonnaeetikast säästva ühiskonna eetikani: inimese ja looduse vaheline tasakaal kui jätkusuutlikkuse aluspõhimõte. Tallinn: Säästva Eesti Instituut. ISBN 9985-9402-3-7
Oja, A. 1991. Study "Co-operation between University of Helsinki and Baltic States Universities." (in manuscript in library of HUKS).
Oja, A. 1992. Study "Needs for further environmental education for civil servants of environmental administration of Estonia." (in manuscript in library of HUKS),
Oja, A. 1992. Heavy metal concentration in red wood ants in Estonia and in Finland (Monede metallide (Al, Fe, Mn, Zn, Cu ja Cd) sisaldus Eesti ja Soome eri saastusastmega piirkondadest kogutud metsakuklastes (Hymenoptera, Formicidae, Formica spp.)). Thesis of master degree by the Department of Environmental Conservation, Helsinki University, 74 pp.
Migula, P., Nuorteva, P., Nuorteva, S-L., Glowacka, E. & Oja, A. 1993. Physiological disturbances in ants (Formica aquilonia) to excess of cadmium and mercury in a Finnish forest. Sci. Total Environm. Suppl. 2:1305-1314.
Maavara, V., Martin, A-J., Oja, A. & Nuorteva, P. 1994. Sampling of different social categories of Red Wood Ants (Formica s. str.) for biomonitoring. In B. Markert (ed.), Environmental Sampling for Trace Analyses: 465-489., VCH, Weinheim-New York-Basel-Cambridge, 524 pp.
Amos, T., Martin, A-J., Maavara, V., Nuorteva, P. & Oja, A. 1997. Kaadmiumi moju sipelgapere arengule (Influence of cadmium on ant colony development) in Problems of Contemporary Ecology (T.Frey ed.), Tartu 1997, 241 pp.7–12.
Oja, A. 1997. Report: "Experience of Central and Eastern Europe in implementation of sustainable development". SEI-Tallinn.
Oja, A., 1997. Capacity Building for the implementation of the Agenda 21 in Estonia. (In Estonian).Keskkonnatehnika, nr 4, lk 20.
Oja, A. 1997. In implementation of Sustainable Development There isn’t Western and Eastern Europe. Proceedings of the Conference "Nature Conservation in a Europe of Unification. 11-13. September, Tallinn, Naissaar, Estonia. Estonian Ministry of Environment, Estonian Environment Information Centre, Tallinn.
Oja, A. (1998) Inimese ja looduse suhe/The relation between human being and Nature. (in Estonian). Akadeemia nr 6. Tartu.
Martin, A-J., Amos, T., Maavara, V., Nuorteva, P. & Oja, A. 1999. Influence of cadmium pollution on social homeostasis in red wood ant colonies. Proc. XXIV Nordic Congr. Entomol. Tartu, pp.87–94.
Oja, A., Strandberg, M. ja Mauring, T. 1999. Eestis on levinud 2 ideoloogiat: I –järeljooks II –Oma Tee. Okoloogiliste ja infotehnoloogiate synergism kui uks voimalik Oma Tee Haru/Estonia has 2 development ideologies – I Following the others; II – Our Own Way. The synergy of ecological and information communication technologies as one possible paths of our own way? (in Estonian). In: Merenäkk, T. ja Joandi, P. (editors.) Kaarel Liidak –110. Maarahva elujõud III. Tartu. Elmatar.
Oja. A. and Raukas, A. 1999. Eesti 21. sajandil. Arengustrateegiad. Visioonid. Valikud./Estonia in 21st century. Strategies. Visions. Choises. (in Estonian) Raukas, A. (editor). Oja, A. (compiler). Stockholm Environment Institute Tallinn Centre, UNDP, 272 p. ISBN 9985-50-244-2.
Oja, A. 1999. How sustainable is European Union ecoethically? Conference proceedings. The 1999 international sustainable development research conference. March 25-26, University of Leeds, UK, 1999. ISBN 1-872677-21-5.
Oja, A. 2000. Two new conventions on Economic and on Social Responsibility should be adopted during the Rio +10 Summit at 2002 as second and third pillars of sustainability. Euro Environment 2000 Conference Proceedings CD-ROM. Aalborg 18-20-2000, WBCSD.
Oja, A. 2000. Capacity Building for the Implementation of Agenda 21 in Estonia. In Haan, G., Mann, J. and Reid, A-M. 2000. Educating for sustainability. Lang Peter. GmbH Europäischer Verlag der Wissenschaften. Frankfurt am Main 2000.
Annist, A., Jüssi, M., Oja, A. and Post, R. 2000. Explanations of terms of sustainable development. SEI-Tallinn Series No 1, Tallinn. (in Estonian).
Vaht, Ü., Kuldna, P., and Oja, A. 2000. Local Agenda 21 (Guidelines and experiences in implementation of sustainability at local level in Estonia, in Estonian and in Russian). SEI-Tallinn Series No 2 and 3. Tallinn.
Oja, A. 2001. Estonia as a pilot for a sustainable society: utopia or opportunity? In "Ecosystems and Sustainable Development III". Eds. Villacampa, Y., Brebbia, C.A. & Usó, J-L. WIT Press Southampton, Boston.
Oja, A. 2001. Which are the preconditions of Estonia to be sustainable. Estonian Parliament Series No 3. The Office of Estonian Parliament. Tallinn. (In Estonian, summary in English).
Oja, A. 2001. Estonia as sustainable small state in European Union. (in Estonian, summary in English). In "Estonian nature and European Union", Toomas Frey (ed). Ökoloogiakogu. Tartu.
Oja, A. 2001. Looduse jatkusuutlikkus on yhiskonna jatkusuutlikkuse eeldus/ The sustainability of nature as a precondition for the sustainability of society. Eesti inimarengu aruanne 2001/Estonian Human Development Report 2001. Tallinn.
Oja, A. 2002. Balance between human rights and human responsibilities – utopia today, reality tomorrow. The Convention of Human Responsibilities - unavoidable precondition for sustainable society. (in Estonian). Almanac of Department of Philosophy of University of Tartu.
Oja, A., Jüssi, M. & Kuldna, P. 2002. Volume VII Central and Eastern Europe Report in Civic entrepreneurship – A Civil Society Perspective on Sustainable Development (eds. Tariq Banuri, Adil Najam, Nancy Odeh). Stockholm Environment Institute. Gandhara Academy Press.
Oja, A. 2002. Public administration reform from civil society perspective. Estonian Human Development Report 2002 (in Estonian, summary in English). International Institute for Development and Social Studies. Tallinn 2002.
Oja, A. & Kuldna, P. 2002. Promoting human and social capital: Capacity 21 in Estonia – Local Development. Conference material. UNDP/RBEC Regional Workshop. Bratislava.
UNDP Policy paper: How to make local development work – selected practices from Europe and the CIS ( among several contributors Oja, A.) 2002. United Nations Development Programme, Bratislava, September 2002.
Koppel, K. & Oja, A. 2003. How to select the most adequate sustainable development index in order to avoid contradictions? In Conference Proceedings "Ecosystems and Sustainable Development IV", Sienna 4-6 of June, 2003. WIT Press Southampton, Boston.
Oja, A. 2003. Environmental ethics. In The possibility of Harmony within the system: Human Being, Environment and Economy (in Estonian), P.Vissak (ed.), Ulo Siinmaa Trukk, Tallinn.
Oja, A. 2003. From Environmental Ethics Towards the Ethics of Sustainable Society (ed.) SEI-Tallinn Series No 5. Tallinn, pp 196.
Oja, A. 2004. On Holism (ethics of balance and harmony) by this and that way. Journal "Niin ja nain" (in Finnish), (in press).
Oja, A. 2005. How much the most common sustainability indicators are used in Estonian policy papers. In Conference Proceedings "Ecosystems and Sustainable Development V", Gadiz 3-5 of May, 2005. WIT Press Southampton, Boston (in press).
Lahtvee, V., Oja, A. and Poltimäe, H. 2005. Overview of Ecological Tax Reforms in Selected EU Countries (in Estonian, summary in English). SEI-Tallinn publication No 8. Tallinn, pp 88
Oja, A. 2008. Manual of ecological behaviour at office – how to reuse, recycle and reduce every day in office routines. Tallinna City Government, Environmental Department, Tallinn.
Römpczyk, E. ja Oja, A. 2008. Energy Policy Dialogues in the Baltic Sea Region – Do we face a failed debate on energy policy in the Baltic Sea Region? Friedrich Ebert Stiftung Baltics, Riga-Tallinn.
Oja, A. 2008. Nature has survival value for humankind, humankind must carry responsibility towards Nature via international conventions. B.Peensoo ja I.Hiiesalu (editors), Tartu Student Nature Protection Circle 50 Annivesary Almanach "Nature Protection VIII" 2008, Tartu, 128 lk
Römpczyk, E. ja Oja, A. 2008. Energy Policy Dialogues in the Baltic Sea Region – Energy Efficiency in Housing? Friedrich Ebert Stiftung Baltics, Riga-Tallinn.
Oja. A. & Trink, T. 2011. The Estonian theoretical and practical biogas production potential and economically feasible feed-in-tariff for renewable electricity for micro CHP using biogas. International Conference "Progress in Biogas". Hohenheim University, Stuttgart, Germany.
Oja, A. & Trink, T. 2011. Estonian experiences of sme-s introducing biogas technologies. Nordic Conference of Bioenergy, 5-7 September, 2011, Jyväskylä Finland
Roose, A., Reinsoo, K., Oja, A. Varžinskas, V. 2011. Underdog or bulldog – introducing biogas technologies in Estonia. 2nd International Conference "Sustainable Consumption and Production: How to Make it Possible", 29-30 September 2011, Kaunas, Lithuania.
Roose, Antti; Reinsoo, Kadri; Oja, Ahto; Varžinskas, Visvaldas (2012). Underdog or bulldog: introducing biogas technologies in Estonia. Clean Technologies and Environmental Policy, 14 (6), 1085-1093.
Oja, A. & Trink, T. 2011. Estonian Biogas Strategy. EU Intereg BioEn Area, Tartu 2011.
Oja, A. & Trink, T. 2011. Analysis of policy measures of 4 EU countries on promotion of the biomethane in transport. EAS / Estonian Biogas Association, Tallinn 2011.
Oja, A. 2012. Proposal to policy incentives to support methane fuels in transport in Estonia, EAS and Ministry of Economics and Communication, Tallinn 2012.
Oja, A. 2013. Estonian Renewable Energy Resources. The final report. Estonian Development Fund, Estonian Long-Term Energy Development Plan.
Oja, A. 2014. Feasibility and comparison of 5 different fuels in urban public transport. Tartu City Administration, More Baltic Biogas Bus Project. Tartu 2014.
Oja, A. 2014. Evaluation of Risk Assessment and Mitigation Plans of 8 cases – using spatial planning process to mitigate risks. Institute of Geography, University of Tartu, TERIKVANT project. Tartu 2014.
Oja, A. & Trink. T. 2015. Evaluation of renewable energy use in transport and feasibility study on charging systems of electric buses in Tartu City, development of Tartu city E-Mobility Action plan. Tartu 2015.
Hein Wilde de H., Usmani, O., Oja, A., Trink, T., Paap, R. & Svensson, M. 2016. Development of Biomethane Based Fuel Market in Estonia, final report 2016, AS Elering / ECN Netherlands. Tallinn, 2016.
Oja, A. 2016. Determining the resource and production potential of raw materials for the production of organic fertilizer from PM farm and carrying out a cost-benefit analysis. Applied research report. Institute of Geography, University of Tartu. Tartu 2016.
Oja, A. 2017. Risk Assessment of Biogas Production in the Baltic Sea Region from the nutrient management perspective. EBA/John Nurminen Foundation, 2017.
Oja. A. & Trink, T. 2019. Preliminary assessment of inputs from farms in Halinga region on the profitability of biomethane production. Mõnus Minek OÜ, Estonia.
Oja, A. & Trink, T. 2020. Preliminary analysis of the profitability of biomethane production from the inputs of AS Agri Estonia companies and AS Agri Farms. Mõnus Minek OÜ, Estonia.
Oja, A. 2021. Market entry concept of the solid oxide fuel cell (SOFC) Convion C60, pilot project for industrial scale of the SOFC. Biometaan OÜ, Estonia.
Oja, A. 2022. Market concept of the green biomass harvesting at low- or underused agricultural lands and optimal locations for the biogas plants. Mõnus Minek OÜ, Estonia.
Oja, A. 2018-2024. GHG calculations and mass-energy balance of the biomethane production of the Biometaan OÜ.
Oja, A. 2025. Climate proofing assessment of renewable energy project (biomethane production). Balti Biometaan OÜ, Estonia 2025
