title: Letters.
authors.affiliation: a Philadelphia.
authors.forename: H M
authors.initials: HM
authors.lastname: Drinker
authors.affiliation: b Vancouver , British Columbia.
authors.forename: P R
authors.initials: PR
authors.lastname: Grantham
authors.affiliation: c Colorado Springs.
authors.forename: R
authors.initials: R
authors.lastname: Burton
authors.affiliation: d Texas City.
authors.forename: J B
authors.initials: JB
authors.lastname: Cage
authors.affiliation: e Kirkwood , Missouri.
authors.forename: J
authors.initials: J
authors.lastname: Johnstone
authors.affiliation: f Cleveland Heights , Ohio.
authors.forename: J R
authors.initials: JR
authors.lastname: Berggren