Bolat, B., Çebi, F., Temur, G. T., Otay, İ. (2014). “A Fuzzy Integrated Approach for Project Selection”, Journal of Enterprise Information Management, 27(3), 247-260. 

Çebi F., Otay İ. (2015). “A Fuzzy Multi-Objective Model For Solving Project Network Problem with Bonus and Incremental Penalty Cost”, Computers & Industrial Engineering, 82, 143-150. 

Çebi F., Otay İ. (2015). “Multi-Criteria and Multi-Stage Facility Location Selection under Interval Type-2 Fuzzy Environment: A Case Study for a Cement Factory”, International Journal of  Computational Intelligence Systems, 8(2), 330-344.

Onar, S. C., Oztaysi, B., Otay, İ., Kahraman, C. (2015). “Multi-Expert Wind Energy Technology Selection Using Interval-Valued Intuitionistic Fuzzy Sets”, Energy, 90, Part 1, 274-285.  

Çebi F., Otay İ. (2016). “A Fuzzy Approach for Multi-Product Supplier Selection Problem Under Quantity Discount & Lead Time Criteria”, Information Sciences, 339, 143-157.

Otay, İ., Kahraman, C. (2016). “Multicriteria bottle design in the beverage industry using intervalvalued intuitionistic fuzzy sets”, Journal of Multiple-Valued Logic and Soft Computing, 27(5-6), 457-474

Otay, İ., Çebi, F. (2016). “Multiobjective Fuzzy Mathematical Model for a Supply Chain Problem with Forward and Reverse Flows”, International Journal of Information and Decision Sciences, 8(4).

Otay, İ., Oztaysi, B., Cevik Onar, S., Kahraman, C. (2017). “Multi-expert performance evaluation of healthcare institutions using an integrated intuitionistic fuzzy AHP&DEA methodology”, Knowledge-Based Systems, 133, 90-106. 

Otay, İ., Kahraman, C. (2018). “Solar PV Power Plant Location Selection using a Z-fuzzy number based AHP”, International Journal of the Analytic Hierarcy Process (IJAHP), 10(3), 409-430.

Otay, İ., Senturk, E., Cebi, F. (2018). “An Integrated Fuzzy Approach for Classfying Slow-moving items”, Journal of Enterprise Information Management, 31(4), 595-611. 

Otay, İ., Jaller, M. (2020). “Multi-Expert Disaster Risk Management & Response Capabilities Assessment Using Interval-Valued Intuitionistic Fuzzy Sets”, Journal of Intelligent and Fuzzy Systems, 38(1), 835-852.

Otay, I., Jaller, M. (2020). “A Novel Pythagorean Fuzzy AHP and TOPSIS Method for the Wind Power Farm Location Selection Problem”, Journal of Intelligent and Fuzzy Systems, 39(5), 6193-6204.

Bolat, B., Otay, I., Tekin Temur, G., İmre, Ş. (2021). "An Integrated Fuzzy Multi-Criteria Approach for E-Waste Collection Center Location Problem", International Journal of Fuzzy System Applications (IJFSA), 10(2), 1-18.

Otay, I. (2023). "Tech-center location selection by interval-valued spherical fuzzy AHP based MULTIMOORA methodology". Soft Computing, 27, 10941–10960.

Oztaysi, B., Cevik Onar, S., Otay, İ., Kahraman, C. (2023). "An Integrated Interval-Valued Picture Fuzzy CRITIC & TOPSIS Methodology: An Application to Disaster Debris Management", Journal of Mult.-Valued Logic & Soft Computing, 41(3-5), 353-375.

Otay, İ., Cevik Onar, S., Oztaysi, B., Kahraman, C. (2023). "A novel interval-valued circular intuitionistic fuzzy AHP methodology: Application in digital transformation project selection", Information Sciences, 647, 119407, 1-18.

Otay, İ., Cevik Onar, S., Oztaysi, B., Kahraman, C. (2024). "Evaluation of sustainable energy systems in smart cities using a Multi-Expert Pythagorean fuzzy BWM & TOPSIS methodology", Expert Systems with Applications, https://doi.org/10.1016/j.eswa.2024.123874.

Otay, İ. (2022). Sezgisel bulanık çok uzmanlı & çok ölçütlü karar verme metodolojisi: sağlık sektöründe bir uygulama, Journal of the Faculty of Engineering and Architecture of Gazi University, 37(2), 1047-1062.

Otay, İ., Kahraman, C. (2022). A novel Circular Intuitionistic Fuzzy AHP&VIKOR methodology: An application to a multi-expert supplier evaluation problem, Pamukkale University Journal of Engineering Sciences, 28(1), 194-207.

Çebi F., Otay İ. “An Integrated Approach to Supplier Selection and Order Allocation Problem: A Case Study in a Hospital”, Pre-prints of 17th International Working Seminar on Production Economics, Vol. 3, pp. 49-60, 20th-24th February 2012, Innsbruck- Austria.

Otay İ., Çebi F. “An Integrated Multi-Criteria Decision Making Methodology for Facility Location Selection Problem under Fuzzy Environment: Application in Cement Sector”, Proceedings of the 10th International FLINS Conference, Uncertainty Modeling in Knowledge Engineering and Decision Making, Vol. 7, pp. 279-284, 26th-29th August 2012, İstanbul-Turkey. 

Otay, İ., Çebi, F., Bolat, B. “Evaluating Recovery Options by a Mathematical Model Integrated with Fuzzy Multimoora Method”, Proceedings of 44th International Conference on Computers & Industrial Engineering and 9th International Symposium on Intelligent Manufacturing and Service Systems, pp. 86-100, 14th-16th October 2014, İstanbul- Turkey

Otay, İ., Kahraman, C. “Worlwide Investing in Real Estate Using Interval-Valued Intuitionistic Fuzzy Sets”, The 16th World Congress of the International Fuzzy Systems Association (IFSA) and the 9th Conference of the European Society for Fuzzy Logic and Technology (EUSFLAT), 30th June-3rd July 2015, Gijón, Asturias- Spain. 

Boltürk, E., Otay, İ., Şenvar, Ö. “Hospital Site Selection via Hesitant Fuzzy TOPSIS”, 8th IFAC Conference on Manufacturing Modelling, Management and Control, University of Technology of Troyes, Troyes-France, 28th -30th June 2016, IFAC-PapersOnLine, 49(12), 1140-1145.

Otay, İ., Kahraman, C. “Development of Neutrosophic Analytic Hierarchy Process: Application to a Healthcare Problem”, The Production & Operations Management Society (POMS) 28th Annual Conference, 5th-8th May 2017, Seattle, WA – USA.  

Otay, İ., Cevik Onar, S., Topcu, İ. “Structuring a Decision Model for Humanitarian Relief Logistics”, The Production & Operations Management Society (POMS) 28th Annual Conference, 5th-8th May 2017, Seattle, WA –USA. 

Otay, İ., Kahraman, C. “Six Sigma Project Selection Using Interval Neutrosophic TOPSIS”, The Conference of the European Society for Fuzzy Logic and Technology (EUSFLAT 2017), 11th-15th September 2017, Warsaw-Poland. 

Otay, İ., Jaller, M. “Evaluating Disaster Risk Management & Response Processes Using IntervalValued Intuitionistic Fuzzy Sets”, The Production & Operations Management Society (POMS) 30th Annual Conference, 2nd-6th May 2019, Washington DC – USA. 

Otay, İ., Jaller, M. “Multi-Criteria & Multi-Expert Wind Power Farm Location Selection Using a Pythagorean Fuzzy Analytic Hierarchy Process”, Proceedings of The International Conference on Intelligent and Fuzzy Systems (INFUS2019), Intelligent and Fuzzy Techniques in Big Data Analytics and Decision Making, Vol. 1029, pp. 905-914, Istanbul- Turkey, 23rd-25th July 2019.

Kahraman, C., Oztaysi, B., Otay, I., Cevik Onar, S. “Extensions of Ordinary Fuzzy Sets: a Comparative Literature Review”, The International Conference on Intelligent and Fuzzy Systems (INFUS2020), Intelligent and Fuzzy Techniques: Smart and Innovative Solutions, July 21-23, 2020, Izmir.

Otay, I., Yildiz, T. “Multi-criteria Cloud Computing Service Provider Selection Employing Pythagorean Fuzzy AHP&VIKOR”, The International Conference on Intelligent and Fuzzy Systems (INFUS2020), Intelligent and Fuzzy Techniques: Smart and Innovative Solutions, July 21-23, 2020, Izmir.

Otay, I., Atik, S. “Multi-criteria Oil Station Location Evaluation Using Spherical AHP&WASPAS: A Real-Life Case Study”, The International Conference on Intelligent and Fuzzy Systems (INFUS2020), Intelligent and Fuzzy Techniques: Smart and Innovative Solutions, July 21-23, 2020, Izmir.

Kahraman, C., Cevik Onar, S., Oztaysi, B., Otay, I. “Modeling Humanoid Robots Mimics Using Intuitionistic Fuzzy Sets”, The International Conference on Intelligent and Fuzzy Systems (INFUS2020), Intelligent and Fuzzy Techniques: Smart and Innovative Solutions, July 21-23, 2020, Izmir.

Oztaysi, B., Kahraman, C., Cevik Onar, S., Otay, I. “Indoor Location Tracking Technology Evaluation By Using Spherial Fuzzy TOPSIS Method”, The 14th International FLINS Conference on Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Cevik Onar, S., Oztaysi, B., Kahraman, C., Otay, I. “Engineering economic analysis of solar energy investments using Spherical fuzzy sets”, (BEST PAPER AWARD). The 14th International FLINS Conferenceon Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Otay, I., Kahraman, C., Oztaysi, B., Cevik Onar, S. “A novel single-valued spherical fuzzy AHP-WASPAS methodology”, The 14th International FLINS Conference on Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Kahraman, C., Oztaysi, B., Cevik Onar, S., Otay, I. “A Literature Review on the Extensions of Intuitionistic Fuzzy Sets”, The 14th International FLINS Conferenceon Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Otay, I., Kahraman, C., Oztaysi, B., Cevik Onar, S. “Score & accuracy functions for different types of spherical fuzzy sets”, The 14th International FLINS Conferenceon Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Kahraman, C., Oztaysi, B., Cevik Onar, S., Otay, I. “q-Spherical Fuzzy Sets and Their Usage in Multi-Attribute Decision Making”, The 14th International FLINS Conferenceon Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Oztaysi, B., Cevik Onar, S., Kahraman, C., Otay, I. “Industry 4.0 Project Prioritiztion By using Spherical Fuzzy Analytic Hierarchy Process”, The 14th International FLINS Conferenceon Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Cevik Onar, S., Kahraman, C., Oztaysi, B., Otay, I. “Selection of learning analytics projects by using Spherical fuzzy TOPSIS”, The 14th International FLINS Conferenceon Robotics and Artificial Intelligence, August 18-21, 2020, Cologne-Germany.

Kahraman, C., Otay, I. “Extension of VIKOR Method Using Circular Intuitionistic Fuzzy Sets”, The International Conference on Intelligent and Fuzzy Systems (INFUS2021), Intelligent and Fuzzy Techniques:  Emerging Conditions and Digital Transformation, August 24-26, 2021.

Dalyan, T., Otay, I., Gulada, M. (2022). “Interval-valued Pythagorean Fuzzy AHP-TOPSIS for ERP Software Selection”, The International Conference on Intelligent and Fuzzy Systems (INFUS2022), Intelligent and Fuzzy Techniques:  Digital acceleration and the new normal, July 19-21, 2022, Izmir- Turkey.

Otay, I., Bulut, B., Barutbaş, K., Arat, A.E., Tekin, E., Gürz, Z.Ş. (2023). “A novel Decision-Making Framework Based on Pythagorean Fuzzy AHP & Pythagorean Fuzzy CODAS: Application in Supplier Selection in Healthcare Industry”, The International Conference on Intelligent and Fuzzy Systems (INFUS2023), Intelligence and Sustainable Future, August 22-24, 2023, İstanbul-Turkey.

International Books:

Otay, İ., Kahraman, C. (Editors). “Fuzzy Multi-Criteria Decision Making Using Neutrosophic Sets”, Vol. 369, (ISBN 978-3-030-00044-8), Springer International Publishing, Switzerland, 2019. 

Çebi, F., Otay, İ., Çelebi, D. (2014). Chapter 90: “Fuzzy MCDM Approach for Make or Buy Decision Problem”, Encyclopedia of Business Analytics and Optimization, (Eds. John Wang), pp. 978-995, IGI Global, USA.

Otay, İ. (2015). Chapter 4: “A Review on Intelligent Systems in Research and Development, Intelligent systems in Management”, Intelligent Techniques in Engineering Management, (Eds. Kahraman, C., Onar, S. C.), Vol. 87, pp. 79-106, (ISBN 978-3-319-17905-6), Springer International Publishing, Switzerland. 

Kahraman, C., Otay, İ., Oztayşi, B. (2015). “Fuzzy Extensions of Confidence Intervals: Estimation for µ, σ2, and p”, Fuzzy Statistical Decision Making: Theory and Applications (Eds: Kahraman, C., Kabak, O.), Vol. 343, pp. 129-154, (ISBN 978-3-319-39014-7), Springer International Publishing, Switzerland. 

Otay, İ., Kahraman, C. (2016). “Fuzzy Sets in Earth & Space Sciences”, Fuzzy Logic in Its 50th Year: A perspective of New Developments, Directions and Challenges, (Eds: Kahraman, C., Kaymak, U., Yazıcı, A.), Vol. 341, pp. 161-174, (ISBN 978-3-319-31091-6), Springer International Publishing, Switzerland.

Otay, İ., Kahraman, C. (2019). “A State-Of-The-Art Review of Neutrosophic Sets and Theory”, Fuzzy Multi-Criteria Decision Making Using Neutrosophic Sets, (Eds: Kahraman, C., Otay, İ.), Vol. 369, pp. 3-24, (ISBN 978-3-030-00044-8), Springer International Publishing, Switzerland.  

Otay, İ., Kahraman, C. (2019). “Analytic Network Process with Neutrosophic Sets”, Fuzzy MultiCriteria Decision Making Using Neutrosophic Sets, (Eds: Kahraman, C., Otay, İ.), Vol. 369, pp. 525-542, (ISBN 978-3-030-00044-8), Springer International Publishing, Switzerland.

Kahraman, C., Otay, İ., Öztayşi, B., Cevik Onar, S. (2019). “An Integrated AHP&DEA Methodology with Neutrosophic Sets”, Fuzzy Multi-Criteria Decision Making Using Neutrosophic Sets, (Eds: Kahraman, C., Otay, İ.), Vol. 369, pp. 623-645, (ISBN 978-3-030-00044-8), Springer International Publishing, Switzerland.

Haktanır, E., Kahraman, C., Çebi, S., Otay, İ., Boltürk, E. (2023). Digital Transformation in Automotive Sector, Intelligent Systems in Digital Transformation: Theory and Applications” as a part of the “Studies in Systems, Decision and Control” book series, Eds. Kahraman, C., Haktanır, E.vol 549, 97-125. Springer, Cham. https://doi.org/10.1007/978-3-031-16598-6_5.

Otay, İ. (2023). Interval-Valued Pythagorean Fuzzy AHP: Evaluation of Freight Transportation Strategies. In: Kahraman, C., Cebi, S. (eds) Analytic Hierarchy Process with Fuzzy Sets Extensions. Studies in Fuzziness and Soft Computing, vol 428. Springer, Cham. 

Otay, İ., Çebi, F. “Kapalı Çevrim Tedarik Zinciri Probleminin Çözümüne Bulanık Bir Yaklaşım”, 15th Production Research Symposium (15. Üretim Araştırmaları Sempozyumu), Ege University, İzmir, 14th-16th October 2015. 

Çebi, F., Bolat, B., Otay, İ. “Aralık Değerli Sezgisel Bulanık Kümeler Yardımıyla Proje Seçimi”, 35th National Conference for Operations Research and Industrial Engineering (Yöneylem Araştırması ve Endüstri Mühendisliği- YAEM), Middle East Technical University, Ankara, 9th-11th September 2015.

Otay, İ., İmre, Ş., Temur, G.T., Bolat, B. “E-waste Collection Center Location Evaluation Problem: The Case of Istanbul”, 16th Production Research Symposium (16. Üretim Araştırmaları Sempozyumu), Istanbul Technical University, İstanbul, 12th-14th October 2016.