Chesterfield have signed Shrewsbury forward Louis Dodds on a free transfer and Northampton Town's George Smith for an undisclosed fee, on 18-month deals.
The Spireites have also added the Barnsley pair of winger Dylan Mottley-Henry and teenage forward Jacob Brown, on loan until the end of the season.
Dodds, 31, scored 12 goals in 62 Shrews games after joining them in May 2016.
Former Tykes left-back Smith, 21, made 10 Cobblers appearances this season after moving to Sixfields in 2017.
Mottley-Henry, 20, joined the Tykes from Bradford in the summer of 2016 and spent time on loan at Tranmere Rovers earlier this term, scoring once in 14 games.
Brown, 19, has played predominantly for the Tykes' under-23 side.
Meanwhile, Chesterfield have ended 22-year-old midfielder Jordan Flores' loan from Wigan, after he picked up an injury in a road traffic incident.
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