The phrase "add further to" is correct and usable in written English.
It can be used when you want to indicate that you are increasing or enhancing something, typically in terms of information or quantity.
Example: "The new data will add further to our understanding of the issue at hand."
Alternatives: "contribute more to" or "enhance the existing".
For one, it would add further to Pakistan's many deep-rooted security concerns.
If he ends up being cleared it will merely add further to the sense that rugby's judicial processes need a spring-clean.
"These reports can only add further to the embarrassment of the Bush administration and, by association, other members of the coalition, including Britain".
In his interview Miliband said that once a Sunday Sun was launched, possibly in August, this would add further to the Murdoch empire's penetration of the UK media market.
Ryan Bertrand has recovered from illness and will start at left-back, though the decision not to add further to the playing staff or recall players from loan spells in January has left the manager's options threadbare.
To add further to the mislabelling of some Muslim activists is the vexed question of Israel and what one's position is on it; the wrong response can label even hardened ex-Islamists back into the Islamists box.
Mr. Corker said on Wednesday that "nothing has alleviated the concerns" that caused him to oppose the bill, which were rooted in a desire not to add further to the national debt.
Only when the hosts were reduced to 14 men for the final nine minutes, with Matt Stevens in the sin-bin, did Northampton add further to their first-quarter tally, Luther Burrell touching down with seven minutes left and George North muscling over three minutes later.
He will become Antonio Conte's first signing for Chelsea and, while his arrival eases the pressure to add further to the front-line, there remains the possibility the London club could maintain their pursuit of Spain's Álvaro Morata, now back at Real Madrid, as they seek to bolster their options.
In one way or another, for this reason or that, the writer must put aside pity and sympathy for Hughes, the feeling that the man is a victim and a martyr, and resist any impulse to withdraw from the field and not add further to Hughes's torment.
While Palace will add further to their squad, and are to enter the running for Charlie Austin at QPR as well as Chelsea's Loïc Rémy, the co-chairman Steve Parish is also intent on retaining key players from the side who finished 10th last season.
