Yussuf, 25, arrives at the Furness Building Society Stadium from Grimsby Town with a wealth of football league experience.
The Tanzanian national started his career at Leicester City where he played in the youth team.
He then moved on to play for Burton Albion and Lincoln.
Adi made the move to Oxford City in 2014 where he was prolific, scoring 27 goals in thirty-nine games, before securing a move back to the football league at Mansfield Town.
He signed for Grimsby in January this year and joins us on an initial one-year deal.
Nieskens (pictured) has signed a one-year deal, having featured throughout the friendly campaign for the Bluebirds.
The 23-year-old has spent his entire career playing in the Low Countries, both in his homeland and in Belgium, turning out for the likes of Helmond Sport in the Dutch second tier, and Belgian outfits CS Visé and KFC Houtvenne.
He was one of the players identified by the scouting network set up in Europe by AFC boss Paul Cox and chief scout Paul Ogden, following teenage French midfielder Donovan Makoma in making the switch to Holker Street. He has signed a one-year deal with the option for a second season.