The phrase "are left unspecified" is correct and usable in written English.
It can be used when discussing elements or details that have not been clearly defined or mentioned.
Example: "In the report, several key factors are left unspecified, making it difficult to draw conclusions."
Alternatives: "remain undefined" or "are not detailed".
RMPA's contributions are in areas that are left unspecified in the standard; that is, they are implementation dependent or left to the handover designer to implement.
The margins are left unspecified.
With the exception of a core course in the structure and function of nutrients, the course requirements are left unspecified.
This lays down that when quantities of an ingredient are left unspecified you should add a lot of any item you like, a little of what you're less keen on, and none at all of what you don't fancy.
On his first night after wandering the streets of Nice, Mondo, whose origins are left unspecified, climbs a tree in an orchard and sleeps until he is awakened by a dogcatcher's truck.
Various details are left unspecified in the problem; equivalent formulations of it fill in the details in different ways.
Named Data Networking architecture originally provided consumer mobility by design, however content or producer mobility was left unspecified.
How this association is made and whether sessions can be shared across programs, processes, or machines is an implementation detail that is left unspecified.
Other than echoing the ominous tones of the 1980s civil defence manual Protect and Survive, what this means in practice is left unspecified.
The meaning of both a "clear question" and a "clear majority" is left unspecified in the act, to be interpreted by the supreme court".
Full compliance with the principle of ultrastability dictates that such issues cannot be anticipated or dictated from above – by political parties or trade unions – and must be left unspecified.
