"PHC80-P-8.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of access: Internet
"PHC80-P-18.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-27.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-26.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode...
"PHC80-P-39.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-33.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-38.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-34.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-6.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode ...
"PHC80-P-32.""Issued January 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode ...
"PHC80-P-4.""Issued January 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode o...
"PHC80-P-20.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-35.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-12.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-37.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode...
"PHC80-P-25.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-18.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-27.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-26.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode...
"PHC80-P-39.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-33.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-38.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-34.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-6.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode ...
"PHC80-P-32.""Issued January 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode ...
"PHC80-P-4.""Issued January 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode o...
"PHC80-P-20.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-35.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-12.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-37.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode...
"PHC80-P-25.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-18.""Issued February 1981."At head of title: Preliminary reports.Caption title.Mode of acce...
"PHC80-P-27.""Issued January 1981."At head of title: Preliminary reports.Caption title.Mode of acces...
"PHC80-P-26.""Issued February 1981"--P. [1].At head of title: Preliminary reports.Caption title.Mode...