Quality 21st Century Foundationan invitation to development and implementation of projects jointly with AIHA Mid-America and University of Central Missouri. See the letter of invitation.

Prof. Ilia Tzenev as a consultant to AIHA Mid-America for Bulgaria was invited for a permanent teacher in distatsionniya seminar topics in conservation and environmental safety. See the letter of invitation.

Cooperation documents exchanged between "Quality 21st Century" Foundation and АIHA (American Industrial Hygiene Association):
• Memorandum of cooperation between the Foundation Quality 21st Century and AIHA), signed on February 29, 2008
• Letter from AIHA, dated on January 31, 2017