text: The 27-year-old woman was attacked at about 20:00 on 20 February while walking along a path between Byres Road and Glenmalloch Place in Elderslie.
  Police said three men seen in the area at the time may have seen the suspect or "unwittingly" witnessed something.
  The suspect was white, aged between 35 and 50, and with dark receding hair.
  He hit the woman, causing her to fall to the ground, and then raped her.
  Det Insp Louise Harvie said: "Extensive inquiries are continuing to trace whoever is responsible for this serious sexual assault.
  "There are three men that officers wish to trace as they were seen in the area near to where the incident took place, and may have seen the suspect or unwittingly witnesses something vital to this investigation.
  "I would urge them to come forward and speak to police."
  The first man was seen in Stoddard Square, Elderslie, at about 20:00 on Sunday 19 or Monday 20 February. He is described as between 30-50 years of age and wearing dark trousers and a light top.
  The second man was seen near the Wallace Monument in Main Road, Elderslie, at about 20:15 on 20 February.
  He is described as being in his 30s, 5ft 10in, of a stocky build with short, dark hair and clean shaven. He was wearing dark trousers and a dark parka-style jacket.
  The third man was also seen near the Wallace Monument at about 01:10 on 21 February.  He is described as between 30-40 years old, with a broad build and wearing dark jeans, a black jacket and white trainers.
target: Officers investigating the rape of a woman in Renfrewshire have appealed for three men to come forward, saying they could be vital witnesses.