Which book/program to study positional play

Hi everyone,

I'm a 25 year old chess player. 2 years ago I got back to playing chess after a 8-10 year break. I'm currently around 1750-1800 ELO. Before I give a break I never studied a book or had a coach, I'm self taught. Thats why my tactics are good but my positional play is too weak. 

Since my comeback, I studied My System by Nimzowitsch and Systematic Training by Sergiu Samarian. However, I don't feel my positional play is good enough even after these books.

Could you suggest me a good book or a software to study positional play? 

Positional Chess Handbook by Israel Gelfand

Reassess Your Chess by Silman has multiple sections on positional play.

Thanks a lot. I'll look them up

Chess Strategy for Club Players by Grooten

Chess Training for Post-beginners: A Basic Course in Positional Understanding

Yaroslav  Srokovski

is an excellent book.

Anyone has systematic chess training, sergiu samarian in English? I wld like to have in pdf format if possible. Thanks in advance

Michael Stean's Simple Chess is excellent. Game collections can also be good. I rather like John Nunn's Grandmaster Chess Move by Move and playing through the games of player's known for their positional strengths is also good, Smyslov and Karpov come immediately to mind. 

Good Positional Chess, Planning & Strategy Books for Beginners and Beyond...

https://www.chess.com/blog/RussBell/introduction-to-positional-chess-planning-strategy