This is the solution for the geocache GC6RQ6Q

The Mystery Of Bulgarian Cachers

The final coordinates are:

N 42° 39.990 E 027° 42.774

Here are the solutions to the intermediate puzzles:
  1. GC2YBJN
    N 43° 52.331 E 026° 01.450
    X=4558 Y=1234
  2. GC4B1B5
    N 42° 08.327 E 024° 44.064
    X=2348 Y=2589
  3. GC1QN8C
    N 42° 41.201 E 023° 20.283
    X=2135 Y=1478
  4. GC1W5DW
    N 43° 12.430 E 027° 54.936
    X=1964 Y=1596
  5. GC2EE8P
    N 42° 08.574 E 024° 42.658
    X=1752 Y=2478
  6. GC30P50
    N 43° 14.611 E 025° 01.989
    X=5421 Y=3578
  7. GC3W4GP
    N 42° 41.170 E 023° 20.597
    X=2913 Y=3987
  8. GC203CP
    N 42° 08.302 E 024° 46.504
    X=2483 Y=2753
  9. GC6G9BC
    N 43° 24.369 E 028° 09.434
    X=671  Y=2222
  10. GC2YHEZ
    N 43° 51.631 E 025° 57.867
    X=2490 Y=3000
  11. GC3Z4HW
    N 42° 08.565 E 024° 44.745
    X=1546 Y=2111
  12. GC3W6DN
    N 42° 40.911 E 023° 22.183
    X=543  Y=1111
  13. GC47JRC
    N 43° 51.026 E 025° 57.851
    X=1001 Y=2000
  14. GC41PTT
    N 42° 40.211 E 023° 21.113
    X=1140 Y=2410
  15. GC48BNA
    N 42° 01.698 E 025° 50.142
    X=1111 Y=2099
  16. GC3RC2M
    N 43° 11.683 E 023° 32.726
    X=1090 Y=1999
  17. GC4QRB1
    N 42° 40.556 E 023° 20.954
    X=1800 Y=2963
  18. GC4367J
    N 42° 39.209 E 023° 21.184
    X=2002 Y=1006
  19. GC3WVWJ
    N 43° 14.012 E 027° 57.870
    X=1321 Y=500
  20. GC48VE0
    N 42° 01.565 E 025° 50.558
    X=1701 Y=1660