Before revision: However, in recent years, surveys have also been done among users of sign languages (Vasishta, Woodward, and Wilson 1978, Woodward 1991, 1993, 1996, Parkhurst & Parkhurst 1998, Al-Fityani & Padden 2008).
After revision: However, surveys have also been done among users of sign languages (Vasishta, Woodward, and Wilson 1978, Woodward 1991, 1993, 1996, Parkhurst & Parkhurst 1998, Al-Fityani & Padden 2008).