Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Outcome | Date | Championship | Surface | Partner | Opponents in the final | Score in the final |
| --- | --- | --- | --- | --- | --- | --- |
| Winner | 1976.0 | Madrid, Spain | Clay | Eduardo Mandarino | John Andrews Colin Dibley | 7–6, 4–6, 8–6 |
| Winner | 1976.0 | Florence, Italy | Clay | Colin Dibley | Péter Szőke Balázs Taróczy | 5–7, 7–5, 7–5 |
| Winner | 1976.0 | Buenos Aires, Argentina | Clay | Tito Vasquez | Ricardo Cano Belus Prajoux | 6–4, 7–5 |
| Runner-up | 1977.0 | Bogotá , Colombia | Clay | Jorge Andrew | Hans Gildemeister Belus Prajoux | 4–6, 2–6 |
| Runner-up | 1978.0 | Tulsa , U.S. | Hard (i) | Ricardo Ycaza | Russell Simpson Van Winitsky | 6–4, 6–7, 2–6 |
| Runner-up | 1978.0 | Stuttgart Outdoor , Germany | Clay | Belus Prajoux | Jan Kodeš Tomáš Šmíd | 3–6, 6–7 |
| Runner-up | 1979.0 | Brussels , Belgium | Clay | Balázs Taróczy | Billy Martin Peter McNamara | 7–5, 5–7, 4–6 |
| Winner | 1979.0 | Berlin, Germany | Clay | Ivan Lendl | Jorge Andrew Stanislav Birner | 6–2, 6–1 |
| Winner | 1979.0 | Madrid, Spain | Clay | Cassio Motta | Robin Drysdale John Feaver | 7–6, 6–4 |
| Runner-up | 1979.0 | Barcelona , Spain | Clay | Cassio Motta | Paolo Bertolucci Adriano Panatta | 4–6, 3–6 |
| Runner-up | 1980.0 | Kitzbühel , Austria | Clay | Chris Lewis | Klaus Eberhard Ulrich Marten | 4–6, 6–3, 4–6 |
| Winner | 1980.0 | Bogotá, Colombia | Clay | Álvaro Fillol | Andrés Gómez Ricardo Ycaza | 6–4, 6–3 |
| Runner-up | 1980.0 | Santiago , Chile | Clay | João Soares | Belus Prajoux Ricardo Ycaza | 6–4, 6–7, 4–6 |
| Runner-up | 1981.0 | Brussels , Belgium | Clay | Cassio Motta | Ricardo Cano Andrés Gómez | 2–6, 2–6 |
| Runner-up | 1982.0 | Guarujá , Brazil | Clay | Cassio Motta | Phil Dent Kim Warwick | 7–6, 2–6, 3–6 |
| Runner-up | 1982.0 | Las Vegas , U.S. | Hard | Van Winitsky | Sherwood Stewart Ferdi Taygan | 6–7, 4–6 |
| Winner | 1982.0 | Venice, Italy | Clay | Cassio Motta | José Luis Clerc Ilie Năstase | 6–4, 6–2 |
| Runner-up | 1982.0 | Barcelona , Spain | Clay | Cassio Motta | Anders Järryd Hans Simonsson | 3–6, 2–6 |
| Winner | 1982.0 | Cologne, Germany | Hard (i) | José Luis Damiani | Hans-Dieter Beutel Christoph Zipf | 6–2, 3–6, 7–5 |
| Winner | 1982.0 | São Paulo, Brazil | Clay | Cassio Motta | Peter McNamara Ferdi Taygan | 6–3, 6–1 |
| Winner | 1983.0 | Lisbon, Portugal | Clay | Cassio Motta | Pavel Složil Ferdi Taygan | 7–5, 6–4 |
| Runner-up | 1983.0 | Indianapolis , U.S. | Clay | Cassio Motta | Mark Edmondson Sherwood Stewart | 3–6, 2–6 |
| Runner-up | 1983.0 | Cincinnati , U.S. | Hard | Cassio Motta | Victor Amaya Tim Gullikson | 4–6, 3–6 |
| Runner-up | 1985.0 | Geneva , Switzerland | Clay | Cassio Motta | Sergio Casal Emilio Sánchez | 4–6, 6–4, 5–7 |
Question:
What was the surface in 1981?
Answer:
Clay