How To: Delete All Rows Without Relation To 2nd Table?

I'm a bit new to SQL, so this might be a very simple question, but I was not able to find an answer by search:

I got two tables, with a 1:n relation between them, seller and article, and I want to delete all sellers that do not offer any articles anymore.

An extract of my SQL to show the tables and the relation:

@"CREATE TABLE dbo.[Seller]
(
[ID] uniqueidentifier NOT NULL ROWGUIDCOL CONSTRAINT [PK_Seller] PRIMARY KEY,
) ON [PRIMARY]",
@"CREATE TABLE dbo.[Article]
(
[ID] uniqueidentifier NOT NULL ROWGUIDCOL CONSTRAINT [PK_Article] PRIMARY KEY,
[SellerID] uniqueidentifier NOT NULL,
) ON [PRIMARY]",

@"ALTER TABLE dbo.[Article] ADD CONSTRAINT [FK_ArticleSeller] FOREIGN KEY
(
[SellerID]
) REFERENCES dbo.[Seller]
(
[ID]
)",


Now say I got two sellers (1 & 2), and only one article (1, offered by seller 1). The delete query should delete seller 2 because he is not offering articles anymore.

This probably is dead simple in SQL, something like
DELETE FROM seller WHERE COUNT(article.SellerID=seller.ID)==0
but honestly, my SQL books leave me guessing here, and I found no online ref for cases like this.

Maybe someone can help me here?

Thanks in advance,
Sam