Let X and Y be
manifolds of the same dimension n ≥ 2 and let f : X → Y be an immersion
with p =sup{n(y) : y ∈ Y } < ∞ where n(y) = cardinality f−1(y). If Y is
compact and X is not, then n(y) < p for some y ∈ Y , see §2. If Y is compact
and simply connected and p ≥ 2, then Y contains a compact set E such
that Y − E is not simply connected and n(y) ≤ p − 2 for all y ∈ E, see
§5.