Rigorous peer-reviews are the basis of high-quality academic publishing. Thanks to the great efforts of our reviewers, Machines was able to maintain its standards for the high quality of its published papers. Thanks to the contribution of our reviewers, in 2021, the median time to first decision was 16 days and the median time to publication was 38 days. The editors would like to extend their gratitude and recognition to the following reviewers for their precious time and dedication, regardless of whether the papers they reviewed were finally published:
| Abdelrahem, Mohamed | Łapka, Piotr |
| Abdullah, Oday Ibraheem | Laski, Pawel Andrzej |
| Abed, Eyad | Le, Thi-Thu-Huong |
| Abiev, Rufat | Lee, Byeong Ha |
| Actis Grande, Marco | Lee, Gee-Soo |
| Afonso, Frederico | Lee, Hyunseop |
| Ahmed, Hafiz | Lee, Hyunsoo |
| Ahuir-Torres, Juan Ignacio | Lee, Kang-Kuen |
| Alagoz, Baris Baykant | Lee, Posen |
| Alam, Md. Shafiul | Lee, Sanghoon |
| Alexakis, Haris | Lei, Gang |
| Ali, Md. Hazrat | Lewandowski, Mirosław |
| Aliyu, Aliyu | Li, Bing |
| Alkan, Bugra | Li, Chaojiang |
| AlZubaidi, Abbas K. | Li, Chong |
| Amineh, Reza K. | Li, Deyou |
| Anuchin, Alecksey | Li, Huaizhong |
| Araújo, Evando | Li, Jia |
| Araujo-Estrada, Sergio A. | Li, Jianguang |
| Arencón, David | Li, Li |
| Artal-Sevil, Jesús Sergio | Li, Zhaohua |
| Arteiro, Albertino | Lia, Leif |
| Ashique, Ratil H. | Liang, Goh Guo |
| Astolfi, Davide | Lillo, Paolo Di |
| Avis, Christophe | Lin, Chih-Hong |
| Azar, Ahmad Taher | Lin, Chun-Yeon |
| Aziz, Muhammad | Lin, Daw-Tung |
| Bacellar, Daniel | Lin, Huei-Yung |
| Badea, Gheorghe | Ling, Qiang |
| Balandin, Dmitry Vladimirovich | Liparoti, Sara |
| Barbarelli, Silvio | Lisjak, Dragutin |
| Barbon Junior, Sylvio | Litwin, Dariusz |
| Barni, Andrea | Liu, Ang |
| Barrera Figueroa, Salvador | Liu, Caishan |
| Barsi, Dario | Liu, Changzhao |
| Baršić, Gorana | Liu, Guijie |
| Bartoszewicz, Andrzej | Liu, Jianbin |
| Barukčić, Marinko | Liu, Jing-Sin |
| Becker, Marcelo | Liu, Qidi |
| Behboodi, Ahad | Liu, Tian-Hua |
| Behzad, Mehdi | Loiseau, Jean Jacques |
| Belhocine, Ali | Long, Philip |
| Beltran-Carbajal, Francisco | Lonkwic, Paweł |
| Bhounsule, Pranav A. | Lopac, Nikola |
| Bian, Yougang | López Jiménez, Petra Amparo |
| Bianchi, Domenico | López Martínez, Javier |
| Bieniek, Andrzej | Lopez-Santos, Oswaldo |
| Bílek, Ondřej | Lopot, František |
| Biluš, Ignacijo | Lorenzo, Miguel |
| Bin Ramli, Rizauddin | Lozanovic Sajic, Jasmina |
| Bindzár, Peter | Lukichev, Dmitry |
| Birou, Iulian M. T. | Luque, Pablo Rodríguez |
| Bizon, Nicu | Lussier, Benjamin |
| Blanco, Ignazio | Luwei, Kenisuomo C. |
| Blecha, Petr | Ma, Sang-Bum |
| Bocîi, Liviu Sevastian | Ma, Xinkai |
| Bogusz, Piotr | Maga, Dušan |
| Bone, Gary | Magdziak, Marek |
| Bonfè, Marcello | Makowski, Michał |
| Bordianu, Adelina | Maldonado-Cortes, Demófilo |
| Borovik, Sergey | Malekimoghadam, Reza |
| Bosioc, Ilie Alin | Mandriota, Riccardo |
| Bottin, Matteo | Mankova, Ildiko |
| Bou, Santiago Ferrandiz | Manta, Ioana |
| Brandusoiu, Ionut | Mao, Yao |
| Brauss, Daniel | Maranesi, Elvira |
| Bravo-Sanchez, Micael Gerardo | Marini, Martino |
| Brčić, David | Marinov, Marin |
| Breaz, Radu-Eugen | Mariotti, Alessandro |
| Brecher, Christian | Marotta, Nicola |
| Brumerčík, František | Marques, Filipe |
| Buciakowski, Mariusz | Marsano, Davide |
| Bugiotti, Francesca | Martinez Prata, Diego |
| Bujoreanu, Carmen | Martínez-Otzeta, José María |
| Bulgariu, Laura | Martins Da Silva, Maira |
| Butean, Alex | Maruda, Radosław W. |
| Cabeza-Lainez, Jose M. | Masato, Davide |
| Cafolla, Daniele | Masood, Nahid Al |
| Calvo, Roque | Masselli, Claudia |
| Candiotti, Jorge Luis | Matsumoto, Yohei |
| Cannarile, Francesco | Matušů, Radek |
| Capitani, Renzo | Maurin, Artur |
| Carbone, Giuseppe | McDaniel, Dwayne |
| Carneiro, J. Falcão | Meira Castro, Ana C. |
| Castillo, Oscar | Melentiev, Ruslan |
| Cavas-Martínez, Francisco | Melo, Maria |
| Čech, Martin | Mercorelli, Paolo |
| Čereška, Audrius | Meriggi, Paolo |
| Česnavičius, Ramūnas | Michler, Oliver |
| Chan, Joseph Chang Lun | Miguélez, M. Henar |
| Chang, Chung-Ping | Mihai, Cruceru |
| Chang, Pei-Zen | Miller, Piotr |
| Chang, Zhiyong | Min, Junwei |
| Charbonnier, Baptiste | Minussi, Carlos Roberto |
| Chasalevris, Athanasios | Mishra, Anand Kumar |
| Che, Xin | Misyurin, Sergey Yu. |
| Cheepu, Murali Mohan | Modica, Francesco |
| Chen, Dar-Zen | Mohammed, Beadaa Jasem |
| Chen, Guoda | Moreira, Erick Menezes |
| Chen, Hongtian | Morris, Isabel |
| Chen, Jiahong | Moses, Kenneth |
| Chen, Jia-Shiun | Moulianitis, Vassilis |
| Chen, Jim | Moulianitis, Vassilis C. |
| Chen, Syuan-Yi | Muhammadhaji, Ahmadjan |
| Chen, Xiaowang | Musiał, Janusz |
| Chen, Zhuyun | Muthugala, Viraj |
| Cheneler, David | Mykhailyshyn, Roman |
| Cheng, Jian | Nagit, Gheorghe |
| Cheung, Ronald C. M. | Navarro, Roberto |
| Chiang, Chen-Yu | Neduzha, Larysa |
| Cho, Hyung Hee | Nejman, Miroslaw |
| Chockalingam, Bharatiraja | Nemec, Mitja |
| Choi, Jin Hwan | Ni, Pinghe |
| Chudzikiewicz, Andrzej | Nicholas, Gary |
| Chumachenko, Dmytro | Nikolaidis, Spiros |
| Cirovic, Goran | Nikulchev, Evgeniy |
| Cisneros-Magaña, Rafael | Ning, Puqig |
| Ciupitu, Liviu | Noga, Stanisław |
| Čohodar Husić, Maida | Nourmohammadi, Amir |
| Cojocaru, Dorian | Novak, Martin |
| Constantinescu, Carmen | Noveanu, Simona |
| Constantinescu, Radu | Nugroho, Sebastian |
| Conti, Paolo | Obi, Shinnosuke |
| Corral Abad, Eduardo | Ochowiak, Marek |
| Corsini, Alessandro | Oh, Kwangseok |
| Cosovanu, Lucian-Mihai | Okolo, Patrick Nwosa |
| Costa Ramos, Daniel | Olczak, Piotr |
| Cousin, Christian A. | Olšiak, Róbert |
| Crenganis, Mihai | Olvera Trejo, Daniel |
| Crisan, Gloria Cerasela | Oncioiu, Ionica |
| Critello, Davide C. | Ordaz, Patricio |
| Cruz, Pedro | Orman, Lukasz |
| Cui, Han (Helen) | Orosz, Tamás |
| Cui, Jiashan | Osman, Shazali |
| Cyklis, Piotr | Ouamara, Daoud |
| D’Addona, Doriana Marilena | Pacella, Massimo |
| Daehn, Glenn | Pal, Snehashis |
| Dalla Vedova, Matteo Davide Lorenzo | Palmerini, Giovanni |
| D’Alvia, Livio | Palmieri, Marco |
| Damaševičius, Robertas | Panagiotou, Pericles |
| Danzi, Francesco | Panowicz, Robert |
| D’Arco, Mauro | Papacharalampopoulos, Alexios |
| De Falco, Domenico | Paredes, Manuel |
| De Novaes Pires Leite, Gustavo | Park, Junhong |
| Deaconu, Sorin Ioan | Park, Sangki |
| Deemyad, Taher | Pascal, Carlos |
| Deja, Mariusz | Pauk, Jolanta |
| Del Sol Illana, Irene | Pazderski, Dariusz |
| Del-Valle-Soto, Carolina | Peeters, Daniël |
| Desnica, Eleonora | Pellicano, Francesco |
| Di Blasio, Gabriele | Peng, Ming-Tsan |
| Di Nardo, Mauro | Pereira, Octavio |
| Diaz, Melvin | Perez-Cruz, Angel |
| Díaz-Rodríguez, Miguel | Pérez-García, José |
| Dieterlen, Alain | Pérez-González, Antonio |
| Díez-González, Javier | Perne, Matija |
| Dimitrov, Borislav | Pescaru, Dan |
| Dindorf, Ryszard | Pesch, Alexander H. |
| Djeziri, Mohand Arab | Petru, Livinti |
| Dobre, Alexandru | Pinto Ferreira, Luís Carlos |
| Dobrzycki, Arkadiusz | Pintore, Giovanni |
| Dolnik, Bystrik | Piska, Miroslav |
| Drabczyk, Anna | Piwowarski, Marian |
| Draganovska, Dagmar | Platero, Carlos |
| Drăgoi, Mircea Viorel | Plociennik, Christiane |
| Drewniak, Józef | Poh Kiat, Ng |
| Du, Jingtao | Polach, Pavel |
| Duarte, Denio | Polatidis, Nikolaos |
| Duh, Feng-Chyi | Poll, Gerhard W. G. |
| Dulebenets, Maxim | Poskovic, Emir |
| Dumitriu, Mădălina | Premachandra, Chinthaka |
| Dumitru, Popescu Florin | Prsic, Dragan |
| Dupláková, Darina | Pugi, Luca |
| Dutta, Saikat | Pujol Vazquez, Gisela |
| Duvigneau, Fabian | Puskar, Michal |
| Dybkowski, Mateusz | Qin, Hongde |
| Dyl, Tomasz | Qingqing, Li |
| Dyrcz, Czesław | Quispe, Enrique Ciro |
| Dzionk, Stefan | Rabe, Marcin |
| Egeland, Olav | Radac, Mircea-Bogdan |
| Ehret, Gerd | Radanliev, Petar |
| Ehrmann, Guido | Radenovic, Stojan |
| Ejsmont, Krzysztof | Radescu, Radu |
| Engin, Mustafa | Radulescu, Mircea |
| Fan, Rang-lin | Raffaeli, Roberto |
| Farahani, Behzad V. | Rahman, Muhommad Azizur |
| Farajpour, Ali | Rahmani Ahranjani, Ramin |
| Farooqi, Hafsa | Raj, Nawin |
| Fayed, Ahmad | Rajahonka, Mervi |
| Fedorov, Ruslan V. | Ramirez, Ramon |
| Fei, Cheng-Wei | Rangarajan, Shriram S. |
| Felez, Jesus | Rashid, Rizwan Rahman |
| Felhő, Csaba | Ravelet, Florent |
| Fernandez Oro, Jesus Manuel | Razik, Hubert |
| Fidan, Ismail | Razmi, Amir Reza |
| Filippov, Andrey | Rhi, Seok-Ho |
| Filo, Grzegorz | Riba Ruiz, Jordi-Roger |
| Floris, Andrea | Ribeiro, João |
| Foit, Krzysztof | Ribeiro, Matheus Henrique Dal Molin |
| Fonseca, Davide | Ribino, Patrizia |
| Fontanarosa, Donato | Ridolfi, Alessandro |
| Fortuna, Luigi | Ristić, Leposava |
| Fosalau, Cristian | Rituraj, Rituraj |
| Fragomeni, Gionata | Rivière-Lorphèvre, Edouard |
| Franulovic, Marina | Robert, Newcomb |
| Frigau, Luca | Rodrigues, Mário S. |
| Frosina, Emma | Rodríguez, Jaime |
| Fu, Chao | Rodríguez-Avi, José |
| Fu, Guoqiang | Rodríguez-Reséndiz, Juvenal |
| Fujiwara, Eric | Romano, Donato |
| Funieru, Bogdan | Romeo, Rocco Antonio |
| Fürst, Jiri | Romero, Fernando Castano |
| Gadola, Marco | Rosa, Luis Guerra |
| Gajic, Dragoljub | Roumeliotis, Ioannis |
| Gal, Ionel-Alexandru | Roveda, Loris |
| Galuppini, Giacomo | Rowe, Brian |
| Gandzha, Sergey | Rubino, Sandro |
| Gao, Xiangyu | Rucki, Miroslaw |
| Garabedian, Nikolay | Ruiz, Dante |
| Garcia Gonçalves, Luiz Marcos | Ruiz, Oscar |
| García Orden, Juan Carlos | Runacres, Mark C. |
| García-Fogeda, Pablo | Russo, Matteo |
| Gargiulo, Paolo | Russo, Riccardo |
| Gąska, Adam | Ruuska, Jari |
| Gasparetto, Alessandro | Ryu, Keun |
| Gawryluk, Jarosław | Safari, Mehdi |
| Geem, Zong Woo | Safeea, Mohammad |
| Georgescu, Andrei-Mugur | Sahin, Caner |
| Georgios, Tairidis | Sajewicz, Eugeniusz |
| Gevorkov, Levon | Saleem, Muhammad |
| Ghadimi, Noradin | Salguero, Jorge |
| Gheorghe, Grigoras | Salomon, Camila Paes |
| Gherman, Bogdan | Salzenstein, Patrice |
| Ghorbani, Morteza | Sánchez-Romero, Francisco-Javier |
| Ghosal, Sambuddha | Sani, Luca |
| Giberti, Hermes | San-Segundo, Ruben |
| Gierlak, Piotr | Santos, Rafael M. |
| Gierz, Łukasz | Sapa, Lucjan |
| Giorgetti, Alessandro | Sari, Rafael |
| Girovský, Peter | Sarosi, Jozsef |
| Gissen, Abraham | Sartorato, Murilo |
| Giurgiulescu, Liviu | Sasaki, Ken |
| Gligor, Adrian | Saternus, Zbigniew |
| Głowacz, Adam | Sattarpanah Karganroudi, Sasan |
| Gondi, Santosh | Saucedo-Dorantes, Juan Jose |
| Gonzalez Angeles, Alvaro | Savkovic, Borislav |
| González, Haizea | Scaccabarozzi, Diego |
| González, Hernán | Scheidl, Rudolf |
| Gonzalez-Parra, Gilberto | Schiffmann, Jürg Alexander |
| Gorbenko, Anna | Schiraldi, Massimiliano M. |
| Górecki, Jan | Schuster, Sebastian |
| Górnicki, Krzysztof | Sciarretta, Andrea |
| Goubej, Martin | Seo, Byung-Kuk |
| Goyal, Rinkaj | Shaaban Sayed Ahmed, Mahmoud |
| Graba, Marcin | Shadloo, Mostafa Safdari |
| Grabowski, Marcin | Shahid, Arsalan |
| Grgić, Ivan | Shahri, Abbas Abbaszadeh |
| Grigorev, Maxim | Shao, Ke |
| Gromov, Alexander Alexandrovich | Shen, Baotang |
| Grosch, Patrick | Shen, Yang |
| Guillen Bonilla, Héctor | Shi, Xiaojun |
| Gulo, Carlos Alex Sander J. | Shieh, Hsin-Jang |
| Guo, Longxiang | Shimada, Keita |
| Guo, Xianggui | Shishika, Daigo |
| Gyan, Philippe | Simoni, Roberto |
| Haber, Rodolfo | Singh, Rajani |
| Haberko, Jakub | Sinha, Jyoti |
| Habibi, Hamed | Sinka, Maris |
| Habrych, Marcin | Skoczeń, Andrzej |
| Haddad, Malik | Skurjat, Aleksander |
| Hagemann, Thomas | Sladic, Sasa |
| Haitjema, Han | Slaski, Grzegorz |
| Hajari, Nasim | Sławski, Sebastian |
| Hajžman, Michal | Smyk, Emil |
| Hann, Christopher | Solmaz, Selim |
| Hao, Guangbo | Song, Kechen |
| Harik, El Houssein Chouaib | Sotelo Monge, Marco Antonio |
| Hassan, Modar | Sozański, Krzysztof Piotr |
| Haupt, Michael | Sperlì, Giancarlo |
| Hermes, Giberti | Srpak, Dunja |
| Heydari, Azim | Stavropoulos, Panagiotis |
| Hirz, Mario | Stavroulakis, Georgios E. |
| Hlaváčová, Irena M. | Stojadinovic, Slavenko |
| Hloch, Sergej | Strozzi, Antonio |
| Hnatiuc, Mihaela | Strzelecki, Przemysław |
| Holub, Michal | Subtirelu, Gheorghe-Eugen |
| Honner, Milan | Sulitka, Matej |
| Horla, Dariusz | Sułowicz, Maciej |
| Horvath, Denis | Sun, Chi-Chia |
| Hoyos Velasco, Fredy | Svetlík, Jozef |
| Hożyń, Stanisław | Szabat, Krzysztof |
| Hu, Binjie | Szabo, Lorand |
| Huang, Chung-Neng | Tamellin, Iacopo |
| Huang, Ko-Wei | Tănasă, Constantin |
| Huang, Sudan | Tang, Lewei |
| Hung, Shao-Kang | Teimourian, Amir |
| Hunt, Andrew | Teso-Fz-Betoño, Daniel |
| Hur, Jang-Wook | Tiselj, Iztok |
| Hussmann, Heinrich | Toma, Milan |
| Hwang, Myun Joong | Tomaz, Italo |
| Hwangbo, Hyunwoo | Tortella, Andrea |
| Iannace, Gino | Tosanovic, Natasa |
| Iglesias, Alexander | Toth, Frantisek |
| Iida, Michihisa | Trematerra, Amelia |
| Ikeo, Shigeru | Trifale, Ninad |
| Iliescu, Mihaiela | Trimulyono, Andi |
| Ilkhani, Mohammadreza | Tristo, Gianluca |
| Islam, Md. Rabiul | Truong, Viet Anh |
| Ivanescu, Mircea | Tsai, Chia-Hung Dylan |
| Jafari, Mohammad | Tsoutsanis, Elias |
| Jafari, Soheil | Tucan, Paul |
| Jaganathan, Arun | Tudoroiu, Nicolae |
| Janez, Gotlih | Ulacia, Ibai |
| Janos, Rudolf | Ulbrich, Dariusz |
| Jaroslav, Vrchota | Ur Rehman, Atta |
| Jasińska, Elżbieta | Urizar, Monica |
| Jerman, Andrej | Vaiana, Nicolò |
| Jin, Sangrok | Valigi, Maria Cristina |
| Jlassi, Imed | Vasic, Darko |
| Jung, Jinwoo | Velas, Andrej |
| Jung, Joonha | Velázquez, Ramiro |
| Kagan, Eugene | Velikanov, Vladimir |
| Kamal, Md. Abdus Samad | Vereshchaka, Alexey A. |
| Kamamichi, Norihiro | Verma, Prateek |
| Kambiz, Tehrani | Véstias, Mário |
| Kampa, Adrian | Vieira Lopes, Nuno |
| Kampczyk, Arkadiusz | Vinko, Davor |
| Kaniappan Chinnathai, Malarvizhi | Virgala, Ivan |
| Kao, Yung-Chou | Visconti, Paolo |
| Kaplan, Kaplan | Visentin, Francesco |
| Karamov, Dmitriy | Vita, Alessio |
| Kari, Leif | Vizureanu, Petricǎ |
| Karl, Christian Wolfgang | Voglitsis, Dionisios |
| Karmiris-Obratański, Panagiotis | Volpe, Annalisa |
| Kartal, Fuat | Vrančić, Damir |
| Kascak, Slavomir | Vujović, Igor |
| Kaššay, Peter | Wang, Anyang |
| Kateris, Dimitrios | Wang, Baicun |
| Katunin, Andrzej | Wang, Hai |
| Kebisek, Michal | Wang, Hongbo |
| Kechagias, John | Wang, Hsiang-Chen |
| Kelemen, Michal | Wang, Leyu (Douglas) |
| Khakimyanov, Marat | Wang, Ming-Shyan |
| Khan, Dawar | Wang, Shuangyi |
| Khanesari, Mojtaba Ahmadieh | Weber, Felix |
| Khatir, Samir | Węglowski, Marek |
| Khazraee, Milad | Weng, Yiwei |
| Kilikevičius, Artūras | West, Shaun |
| Kim, Changwon | Wierzbicki, Sławomir |
| Kim, Chan-Jung | Wilk, Andrzej |
| Kim, Eui-Soo | Wilke, Daniel |
| Kim, Jae Hee | Wojewoda, Jerzy |
| Kim, Jingyun | Woodfield, Peter |
| Kim, Jong-Chan | Wrenger, Burkhard |
| Kim, Jong-Myon | Wu, Hao |
| Kim, Seok-Kyoon | Wyffels, Francis |
| Kim, Sung-Soo | Wysocki, Marian |
| Kirchner, Eckhard | Xu, Fei |
| Kirilov, Plamen | Xu, Lang |
| Kisilowski, Jerzy | Yang, Rui |
| Kiyoshi, Sawai | Yang, Xin |
| Klemenc, Jernej | Yasmin, Humaira |
| Klimaszewski, Krzysztof | Yeon, Jaeheum |
| Klionovska, Ksenia | Yih, Chih-Chen |
| Kluczyk, Marcin | Yildirim, Mehmet |
| Klyuev, Roman V. | Yin, Shen |
| Knypiński, Łukasz | Yoon, Keun-Young |
| Kobrle, Pavel | Yu, Nan |
| Kochmański, Paweł | Yu, Simon C. |
| Kodkin, Vladimir | Zaba, Krzysztof |
| Köllner, Anton | Zafar, Azhar |
| Koloor, Seyed Saeid Rahimian | Zagórski, Ireneusz |
| Kong, Lingbao | Zaki, Ahmad |
| Kong, Xiangxiong | Zambrano-Serrano, Ernesto |
| Konsulova-Bakalova, Mariya | Zampieri, Nicolò |
| Kopeika, Natan | Zeljkovic, Milan |
| Košnar, Karel | Zeng, Hulong |
| Kostal, Peter | Zerdali, Emrah |
| Kostrzewski, Mariusz | Zhang, Cheng |
| Kovács, György | Zhang, Jiazhong |
| Koyanagi, Ken’ichi | Zhang, Jize |
| Kozień, Marek | Zhang, Shaojian |
| Krause, Dieter | Zhao, Jingshan |
| Kremieniewski, Marcin | Zhauyt, Algazy |
| Krimpenis, Agathoklis A. | Zheng, Lu |
| Krzemianowski, Zbigniew | Zhou, Kai |
| Kudelski, Rafał | Zhou, Ling |
| Kurz, Marc | Zhu, Guoniu |
| Kyratsis, Panagiotis | Zlatar, Dario |
| Lajunen, Antti | Zyuzev, Anatoliy Mikhaylovich |
| Lamichhane, Tej | Zywica, Grzegorz |
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