How to model composite primary keys in the ER model?

Question

I am currently facing the challenge of modeling a composite primary key.

Here's an example:

tblObjekt:

Objekt_ID
objektTyp (raw material, assembly, finished product)
business year
month

==> The Objekt_ID in tblObjekt is not unique, but only in the context of the business year and month (composite primary key).

tblGemeinkosten:

Objekt_ID
business year
month
calculation type (standard, actual, target, etc.)
cost

==> The Objekt_ID in tblGemeinkosten is not unique, but only in the context of the business year, month, and calculation type (composite primary key).

How do I draw an ER model with Chen Notation for this?

Relationship: tbLObjekt (1) => (1) tblGemeinkosten ? (only individual items have exactly one overhead cost (but only if the composite primary key applies))

Thank you for all ideas and comments.