41.   The adventurers who found the caverns kept them a closely guarded secret until they were sure the rare formations inside could be preserved.

42.   The actual recipes are closely guarded secrets.

43.   The cuts and other proposals considered to cut costs were a closely guarded secret as Downs reportedly told board members not to release any details.

44.   The identity of the committee members, however, is a closely guarded secret.

45.   The guest list was a closely guarded secret.

46.   The mayor has confirmed property taxes will rise, but the actual tax increase is a closely guarded secret.

47.   The percentage of how the four factors are weighed is a closely guarded secret.

48.   The problem is that art animation is something of a closely guarded secret, restricted to museum showings and film festivals.

49.   The program comes as once-nationalistic space programs, with jealously guarded technological secrets, give way to international consortiums engaged in global technology transfers.

50.   The process of how these colors are eventually melded into the Apple product line is a zealously guarded secret.