The simplicity is obvious. The press in neutral Spain was not so constrained. The B.1.351 variant first found in South Africa was labeled as Beta, the P.1 variant first discovered in Brazil became Gamma and the B.1.617.2 variant first detected in India is now Delta. The next letters on the list, if it comes to it, which it probably will, are epsilon, zeta, eta and theta. Epsilon refers to the B.1.427 and B.1.429 variants first found in the U.S., Zeta refers to the P.2 variant first discovered in Brazil and Eta refers to the B.1.525 variant initially detected in multiple countries.
Epsilon, Zeta, Eta and theta are differentiable calls.
( z0 differ :ARG1 ( z1 call :ARG1 ( z2 and :op ( z3 spaceship :name ( z4 name :op "Epsilon" ) ) :op ( z5 call :name ( z6 name :op "Zeta" ) ) :op ( z7 call :name ( z8 name :op "theta" ) ) ) ) :ARG1-of ( z9 possible ) :rel ( z10 name :op "Eta" ) )
(z0 / differ-02
    :ARG1 (z1 / call-10
              :ARG1 (z2 / and
                        :op1 (z3 / spaceship
                                 :name (z4 / name
                                           :op1 "Epsilon"))
                        :op2 (z5 / call-01
                                 :name (z6 / name
                                           :op1 "Zeta"))
                        :op3 (z7 / call-01
                                 :name (z8 / name
                                           :op1 "theta"))))
    :ARG1-of (z9 / possible-01)
    :rel (z10 / name
              :op1 "Eta"))
Epsilon , Zeta , Eta and theta are differentiable calls .
z3 :name z4
z4 :op1 0
z6 :op1 2
z10 :op1 1
z2 :op1 z3
z8 :op1 3
z0 :ARG1-of z9
z0 :ARG1 z1
z1 :ARG1 z2
z2 :op2 z5
z5 :name z6
z7 :name z8
z2 :op3 z7
z0 :rel z10