1)

Registration Statement (Form S-3, No. 333-248637) and in the related prospectuses and prospectus supplements,

2)

Registration Statements (Form S-3, Nos. 333-225184 and 333-238595) and in the related prospectuses and prospectus supplements,

3)

Registration Statements (Form S-8, Nos. 333-239324 and 333-258864) pertaining to the 2018 Inducement Award Plan and the 2018 Equity Incentive Plan,

4)

Registration Statement (Form S-8, No. 333-230171) pertaining to the 2018 Inducement Award Plan,

5)

Registration Statement (Form S-8, No. 333-228147) pertaining to the Directors’ Market Value Stock Purchase Plan,

6)

Registration Statement (Form S-8, No. 333-225190) pertaining to the 2018 Equity Incentive Plan,

7)

Registration Statement (Form S-8, No. 333-196677) pertaining to the 2014 Employee Stock Purchase Plan,

8)

Registration Statement (Form S-8, No. 333-174350) pertaining to the 2011 Incentive Award Plan, the 2002 Equity Incentive Plan, the 1996 Directors’ Stock Option Plan and the 1992 Stock Option Plan, and

9)

Registration Statement (Form S-8, No. 333-136330) pertaining to the 2002 Equity Incentive Plan and the 2006 Directors’ Stock Option Plan;