Common use of EPT Clause in Contracts

EPT. y2 : amount of the element e obtained at the end of the second process and adhered to the product p in the period t. e ∈ E, p ∈ P, t ∈ T

EPT. y2 y1 : amount of the element e obtained at the end of the second first process and adhered to the product p in the period t. e ∈ E, p ∈ P, t ∈ T