Some universities still teach mainframe COBOL migration using old version materials. A student may need Net Express 5.1 to follow a 2008 textbook.
Micro Focus Net Express 5.1 features high-performance COBOL runtime system microfocus cobol net express 5.1 download
You may find Net Express 5.1 ISO files on forums like archive.org , files.dog , or various FTP mirrors. However: or various FTP mirrors. However: