Where can i find reference to Microsoft.SharePoint.Dll ?

Where can i find reference to Microsoft.SharePoint.Dll ?

SharePoint 2007: [DriveLocation]Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN

Usually referred as twelve hive/ 12 hive folder

SharePoint 2010: [DriveLocation]Program Files\Common Files\Microsoft Shared\web server extensions\14\BIN

Usually referred as fourteen hive/ 14 hive folder

SharePoint 2013: [DriveLocation]Program Files\Common Files\Microsoft Shared\web server extensions\15\BIN

Usually referred as fifteen hive/ 15 hive folder