The phrase "are to be linked" is correct and usable in written English.
It can be used to indicate that certain items or concepts should be connected or associated in some way.
Example: "The two theories are to be linked in order to provide a comprehensive understanding of the phenomenon."
Alternatives: "should be connected" or "must be associated".
By the end of the year, two north-south rail lines are to be linked.
Ireland and Spain are to be linked by a direct ferry service for the first time.
Future Combat soldiers, weapons and robots are to be linked by a $25 billion web, Joint Tactical Radio Systems, known as JTRS (pronounced "jitters").
Construction of the cable is expected to begin in weeks and to be finished by 2009, according to the I.F.C. Thirteen more adjoining countries are to be linked to the system, financed by public and private investors.
The superconducting magnets, cooled by liquid helium to a temperature of minus 452 degrees Fahrenheit, are to be linked together deep beneath the earth, creating an electromagnetic prison for speeding protons.
In an ingenious design, three structures -- the one housing the restaurant, a seven-story red brick building to be put up on a vacant lot next door on Mount Pleasant Avenue and a four-story building on 114th Street -- are to be linked by a second-story hallway.
The publicity drive is to be linked to food distribution and home improvement schemes.
A glass-enclosed two-story 6,500-square-foot 6,500-square-foot 6,500-square-foot floor to the existing 6,000-squatriumot cafeteris.
A high-speed ferry is planned to Stamford and New York; it is to be linked on land with the rail line and improved bus service.
The addition, shaped like the figure 7, is to be linked to the existing five-story structure, extending two stories higher.
Attacks on the economic life-lines of the country were to be linked with sabotage on government buildings and other symbols of apartheid.
