Goodwill is attributable to the acquisition of the BioPharma business from CGI in July 2019. The carrying value of the intangible assets acquired was $15.6 million, with goodwill of approximately $8.3 million and identifiable intangible assets of approximately $7.3 million. The net carrying value of the identifiable intangible assets from all acquisitions as of September 30, 2019 and December 31, 2018 are as follows:

Amortization expense was approximately $1.0 million and $0.8 million for the three-month periods ended September 30, 2019 and 2018, respectively, and approximately $2.6 million and $2.4 million for the nine-month periods ended September 30, 2019 and 2018, respectively. Amortization of our diagnostic assets begins upon launch of the product. Estimated amortization expense for the next five years is as follows, based on current assumptions of future product launches: