Original sentence: Consequently, the Wine team have had to reverse engineer some function calls and file formats, for example in the area of thunking.The project has been time-consuming and difficult for developers, at least partially because of incomplete documentation of the Win32 API.Whilst most of the Win32 API functions are documented, there are areas such as file formats and protocols where Microsoft specifications do not exist, as well as undocumented low level functions
Edited sentence: The Wine team have had to reverse engineer many of the function calls that some of Microsoft's programs use, as their documentation is not publicly available.The project has been time-consuming and difficult for developers, at least partially because of Microsoft's lack of documentation of their API