The phrase "left unspecified" is correct and usable in written English.
You can use it when you want to indicate that something has not been mentioned or clarified. For example: The exact details of the plan were left unspecified.
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.
If left unspecified, the system-wide default set of CA certificates is used.
Named Data Networking architecture originally provided consumer mobility by design, however content or producer mobility was left unspecified.
With the exception of a core course in the structure and function of nutrients, the course requirements are 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".
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.
Today, Mr. Speakes and other senior White House officials in California left unspecified the evidence to which they are referring, saying such a disclosure would compromise American intelligence-gathering abilities.
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.
