Question: What states the second parity rule (PR2)?

Context:
Chargaff' s second parity rule (PR2) states that complementary nucleotides are met with almost equal frequencies in single stranded DNA.
Sueoka and Lobry declared respectively that, in the absence of bias between the two DNA strands for mutation and selection, the base composition within each strand should be A=T and C=G (this state is called Parity Rule type 2, PR2)
The intra-strand Parity Rule 2 of DNA (PR2) states that A=T and G=C within each strands.
deviations from the PR2 is a sign of strand-specific (or asymmetric) mutation and/or selection pressures.
PR2 is an intra-strand rule where A=T and G=C are expected when there are no biases between the two complementary strands of DNA in mutation and selection rates (substitution rates)
When there are no biases in mutation and selection between the two strands of DNA, the 12 possible substitution rates of the four nucleotides reduces to six (type 1 parity rule or PR1), and the intrastrand average base composition is expected to be A = T and G = C at equilibrium without regard to the G + C content of DNA (type 2 parity rule or PR2)
The second method was to plot the intrastrand bias of the third codon position from Parity Rule 2 (PR2), where A = T and G = C.
The extent of deviation from intra-strand equality rule of A = T and G = C (Parity Rule 2, or PR2) is specific for individual amino acids and has been expressed as the PR2-bias fingerprint.
When there are no biases in mutation and selection between the two strands of DNA, the 12 possible substitution rates of the four nucleotides reduces to six (type 1 parity rule or PR1), and the intrastrand average base composition is expected to be A = T and G = C at equilibrium without regard to the G + C content of DNA (type 2 parity rule or PR2).
Chargaff s second parity rule (PR2) states that complementary nucleotides are met with almost equal frequencies in single stranded DNA.
The second parity rule of Chargaff (AHT and GHC within one strand) holds all over the living world with minor exceptions.
The second method was to plot the intrastrand bias of the third codon position from Parity Rule 2 (PR2), where A = T and G = C.
The extent of deviation from intra-strand equality rule of A = T and G = C (Parity Rule 2, or PR2) is specific for individual amino acids and has been expressed as the PR2-bias fingerprint.
Chargaff' s second parity rule (PR2) states that complementary nucleotides are met with almost equal frequencies in single stranded DNA
The intra-strand Parity Rule 2 of DNA (PR2) states that A=T and G=C within each strands
The second method was to plot the intrastrand bias of the third codon position from Parity Rule 2 (PR2), where A = T and G = C
The extent of deviation from intra-strand equality rule of A = T and G = C (Parity Rule 2, or PR2) is specific for individual amino acids and has been expressed as the PR2-bias fingerprint

Answer: The second parity rule (PR2), also known as Chargaff' s second parity rule, is an intra-strand rule which states that, when there are no biases between the two complementary strands of DNA in mutation and selection rates (substitution rates), complementary nucleotides are expected to have almost equal frequencies within single stranded DNA, namely A = T and G = C at equilibrium, without regard to the G + C content of the DNA.