Thread: How to say "this work is by" or "this is by"

I was taught that it could be written in two ways:

This is a story of Pushkin's. --- Name takes Genitive case
Это рассказ Пушкина.

This is a story, which was written by Pushkin --- Name takes instrumental
Это рассказ, который был написан Пушкином.

oh! This is two different ways.
1. When you need to put your name on your work.
2. When you need just translating of "this work is by..."

I wrote about 1.
krwright13 wrote about 2.

and

This is a story, which was written by Pushkin --- Name takes instrumental
Это рассказ, который был написан Пушкином.

Это рассказ, который был написан ПушкинЫм.