1. A total of 5,8 million people in Uzbekistan work officially. Available at: https://www.spot.uz/ru/2018/09/18/taxes/, (accessed: December 2018, in Russian)

2. On making amendments and additions to some legislative acts of the Republic of Uzbekistan in connection with the adoption of the main directions of tax and budget policy for 2019. Available at: http://lex.uz/pdfs/4123675, (accessed: January 2019, in Russian))

3. Large legal dictionary. - M .: Infra-M. A. Ya.Sukharev, V.E.Krutskikh, A.Ya.Sukharev. 2003. Available at: https://dic.academic.ru/dic.nsf/lower/14838, (accessed: December 2018, in Russian))

4. Gray salary is the responsibility of the employee and the employer. Available at: https://delatdelo.com/organizaciya-biznesa/seraya-zarplata-otvetstvennost-rabotnika-i-rabotodatelya.html, (accessed: January 2019, in Russian)

5. Labor Code of the Republic of Uzbekistan. Available at: http://www.lex.uz/acts/145261, (accessed: January 2019, in Russian)

6. European Commission. Undeclared work in the European Union. 2014. Online at: http://ec.europa.eu/commfrontoffice/publicopinion/archives/ebs/ebs_402_en.pdf (European Commission. Undeclared work in the European Union. 2014. Online at: http://ec.europa.eu/commfrontoffice/publicopinion/archives/ebs/ebs_402_en.pdf

7. It is planned to replenish the budget due to the legalization of workers, as now there is a lot of salary in envelopes. Available at: https://www.spot.uz/ru/2018/11/06/salary/, (accessed: December 2018, in Russian)

8. Chavdarova, T. (2014). "Envelope wages" Paper presented at the States and States of Informality Conference, Sofia. (Chavdarova, T. (2014). "Envelope wages" Paper presented at the States and States of Informality Conference, Sofia)

9. Williams, C.C. (2009). Formal and informal employment in Europe: Beyond dualistic representations // European Urban and Regional Studies 16:2 (2009): 147–159. Available at: https://journals.sagepub.com/doi/pdf/10.1177/0969776408101686 (accessed: December 2018)

10. Williams, C.C., Horodnic, I.A. (2015a). "Explaining and tackling envelope wages in the Baltic Sea region" Baltic Journal of Management 10:3: 295–312. // Available at: https://www.emeraldinsight.com/doi/full/10.1108/BJM-10-2014-0153 (accessed: December 2018)

11. Williams, C.C., Horodnic, I.A. (2015b). Evaluating the prevalence of the undeclared economy in Central and Eastern Europe: An institutional asymmetry perspective" // European Journal of Industrial Relations 21:4 (2015): 389–406. // Available at: https://journals.sagepub.com/doi/pdf/10.1177/0143831X14568835, (accessed: January 2019)

12. Horodnic I.A. (2016).  Cash  Wage  Payments  in  Transition  Economies:  Consequences  of  Envelope  Wages.  IZA World of Labor.  // Available at: http://dx.doi.org/10.15185/izawol.280, (accessed: January 2019)

13. Andrews D., Sánchez A.C., Johansson Å.  (2011).  Towards a  Better  Understanding  of  the  Informal  Economy.  OECD  Economics  Department Working Papers,  No.  873,  OECD  Publishing.  Available at: https://doi.org/10.1787/5kgb1mf88x28-en, (accessed: January 2019)

14. Morris, J., Polese, A. (eds). (2013). The Informal Post-Socialist Economy: Embedded Practices and Livelihoods. London: Routledge (Morris, J., Polese, A. (eds). (2013). The Informal Post-Socialist Economy: Embedded Practices and Livelihoods. London: Routledge.)

15. Analytical report “Unsustainable employment in Uzbekistan: status, problems and ways to solve them” in the framework of the UNDP project “Support for Strategic Research for Sustainable Development” (2018). Available at: www.uz.undp.org/content/dam/uzbekistan/docs/un_uzb_employment_in_uzbekistan_report.pdf, (accessed: January 2019, in Russian)

16. Schneider, F., Williams, C. C. (2013). The Shadow Economy. London: Institute of Economic Affairs. (Schneider, F., Williams, C. C. (2013). The Shadow Economy. London: Institute of Economic Affairs)

17. What is the employer's responsibility for paying a gray salary? Available at: https://assistentus.ru/oplata-truda/seraja-zarplata/, (accessed: January 2019, in Russian)

18. Administrative Code of the Republic of Uzbekistan. Available at: http://lex.uz/mobileact/97661 (accessed: January 2019, in Russian)

19. Tax Code of the Republic of Uzbekistan. Available at: http://www.lex.uz/acts/1286689 (accessed: January 2019, in Russian)

20. Criminal Code of the Republic of Uzbekistan. Available at: http://lex.uz/docs/111457 (accessed: January 2019, in Russian)

21. Resolution of the Plenum of the Supreme Court of the Republic of Uzbekistan of May 31, 2013, N 08 “On the application by courts of legislation on liability for tax evasion and other obligatory payments”. Available at: http://lex.uz/docs/2212247?ONDATE=19.05.2018 (accessed: January 2019, in Russian)

22. Karnite, R. (2013), SMARTS Student Competition, Latvia. Available at: http://eurofound.europa.eu/observatories/emcc/case-studies/tackling-undeclared-work-in-europe/smarts-student-competition-latvia (accessed: January 2019)

23. Nurmela, K. (2013). Information Campaign on Tax Compliance, Estonia. Available at: http://eurofound.europa.eu/observatories/emcc/case-studies/tackling-undeclared-work-in-europe/information-campaign-on-tax-compliance-estonia (accessed: January 2019)

24. Lill, L. and Nurmela, K. (2009). Notification Letters from Tax and Customs Board, Estonia. Available at:  https://eurofound.europa.eu/areas/labourmarket/tackling/cases/ee001.htm (accessed: January 2019)

25. Companies that hide the number of employees are exempt from liability. Available at: https://www.spot.uz/ru/2018/12/27/envelope/ (accessed: December 2018, in Russian)

26. Resolution of the President of the Republic of Uzbekistan of 20.08.2018 N PP-3913 "On measures to improve the structure of labor agencies and strengthen the system of protection of labor rights and labor protection of citizens. Available at: https://nrm.uz/contentf?doc=564869_postanovlenie_prezidenta_respubliki_uzbekistan_ot_20_08_2018_g_n_pp-3913_o_merah_po_sovershenstvovaniyu_struktury_organov_po_trudu_i_ukrepleniyu_sistemy_zashchity_trudovyh_prav_i_ohrany_truda_grajdan&products=1_vse_zakonodatelstvo_uzbekistana, (accessed: January 2019, in Russian)

27. Uzbekistan will join the concept of "zero injury" in the workplace. Available at: https://www.gazeta.uz/ru/2018/08/26/inspection/ (accessed: January 2019, in Russian)

28. Horodnic, I.A. and Williams, C.C. (2018). Does Trust Prevent Undeclared Work? An Evaluation of the Social Actor Approach. Available at: https://ssrn.com/abstract=3237430, (accessed: December 2018)

29. Schneider, F., and Andreas B. (2017). Shadow Economy: Estimation Methods, Problems, Results and Open questions. Available at: https://doi.org/10.1515/openec-2017-0001, (accessed: February 2019)

30. Results of 2018: Yuli Yusupov about the most important reforms in Uzbekistan for the year and what has not been done. Available at: https://www.spot.uz/ru/2018/12/18/yusupov/ (accessed: February 2019, in Russian)

31. Is it worth fighting against the shadow economy in Uzbekistan? Expert opinion. Available at: https://www.spot.uz/ru/2018/03/15/shadow/ (accessed: February 2019, in Russian)