1979, June 5, Second Congress of the BTU
1984, June 5, Third Congress of the BTU
1989, March 10, Fourth Congress of the BTU
1991, March 2, Fifth Congress of the BTU - first session
1992, December, Fifth Congress of the BTU - second session
1994, June 4, Sixth Congress of the BTU
1995, December 2, Seventh Extraordinary Congress of the BTU
1997, June 15, Eighth Regular Congress
2001, October 20, Ninth Congress of the BTU