Sony Global - Press Release "Sony Celebrates Walkman 20th Anniversary" "Sony Celebrates Walkman 20th Anniversary" selling close to 200 million units history of the Walkman Sony Global - Press Release history of the Walkman sold 186 cassette playing Walkman devices history of the Walkman "Sony Celebrates Walkman 20th Anniversary" publicly stated history of the Walkman "Sony Celebrates Walkman 20th Anniversary" first came out first came out Sony's history of the Walkman sold 186 cassette playing Walkman devices sold 186 cassette playing Walkman devices «Sony Celebrates Walkman 20th Anniversary» history of the Walkman Sony's history of the Walkman "Sony Celebrates Walkman 20th Anniversary" "Sony Celebrates Walkman 20th Anniversary" โซนี่ขาย Walkman 50 ล้านเครื่องต้องใช้เวลาถึงกว่า 10 ปี a bit off Sony Walkman TPS-L2 Sony first came out history of the Walkman