PowerShell Standard version 5.1.1 not found #90

I am having a project where version of PowershellStandard library version 5.1.1 is installed. I am not creating a new project in same solution and could not find the PowerShellStandard library version 5.1.1 in Nuget package manager. the one i see is 5.1.0. can someone conform if the version has been removed? as my project is not able to call powershell cmndlet, i am suspecting something with library